Users should not have to search and replace in Heroku install

[ghost]

I had to manually substitute fields an it was unclear was values should have been used.
Script should take in list of settings and finish deploy. Users should not have to search and replace in setting strings.

build dump crash:

-----> Apt app detected
-----> Updating apt caches
       Get:1 http://archive.ubuntu.com/ubuntu xenial InRelease [247 kB]
       Get:2 http://apt.postgresql.org/pub/repos/apt xenial-pgdg InRelease [41.5 kB]
       Get:3 http://archive.ubuntu.com/ubuntu xenial-security InRelease [102 kB]
       Get:4 http://archive.ubuntu.com/ubuntu xenial-updates InRelease [102 kB]
       Get:5 http://archive.ubuntu.com/ubuntu xenial/main amd64 Packages [1,558 kB]
       Get:6 http://apt.postgresql.org/pub/repos/apt xenial-pgdg/main amd64 Packages [98.8 kB]
       Get:7 http://archive.ubuntu.com/ubuntu xenial/universe amd64 Packages [9,827 kB]
       Get:8 http://archive.ubuntu.com/ubuntu xenial-security/main amd64 Packages [417 kB]
       Get:9 http://archive.ubuntu.com/ubuntu xenial-security/universe amd64 Packages [188 kB]
       Get:10 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages [774 kB]
       Get:11 http://archive.ubuntu.com/ubuntu xenial-updates/universe amd64 Packages [648 kB]
       Fetched 14.0 MB in 2s (6,394 kB/s)
       Reading package lists...
-----> Fetching .debs for libssl-dev
       Reading package lists...
       Building dependency tree...
       The following additional packages will be installed:
         libssl1.0.0
       The following packages will be upgraded:
         libssl-dev libssl1.0.0
       2 upgraded, 0 newly installed, 0 to remove and 146 not upgraded.
       Need to get 2,426 kB of archives.
       After this operation, 0 B of additional disk space will be used.
       Get:1 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 libssl-dev amd64 1.0.2g-1ubuntu4.8 [1,345 kB]
       Get:2 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 libssl1.0.0 amd64 1.0.2g-1ubuntu4.8 [1,081 kB]
       Fetched 2,426 kB in 0s (3,352 kB/s)
       Download complete and in download only mode
W: --force-yes is deprecated, use one of the options starting with --allow instead.
-----> Fetching .debs for libpq-dev
       Reading package lists...
       Building dependency tree...
       The following additional packages will be installed:
         libpq5
       Suggested packages:
         postgresql-doc-9.6
       The following packages will be upgraded:
         libpq-dev libpq5
       2 upgraded, 0 newly installed, 0 to remove and 146 not upgraded.
       Need to get 340 kB of archives.
       After this operation, 4,096 B of additional disk space will be used.
       Get:1 http://apt.postgresql.org/pub/repos/apt xenial-pgdg/main amd64 libpq-dev amd64 9.6.3-1.pgdg16.04+1 [212 kB]
       Get:2 http://apt.postgresql.org/pub/repos/apt xenial-pgdg/main amd64 libpq5 amd64 9.6.3-1.pgdg16.04+1 [128 kB]
       Fetched 340 kB in 0s (5,874 kB/s)
       Download complete and in download only mode
W: --force-yes is deprecated, use one of the options starting with --allow instead.
-----> Installing libpq5_9.6.3-1.pgdg16.04+1_amd64.deb
-----> Installing libpq-dev_9.6.3-1.pgdg16.04+1_amd64.deb
-----> Installing libssl1.0.0_1.0.2g-1ubuntu4.8_amd64.deb
-----> Installing libssl-dev_1.0.2g-1ubuntu4.8_amd64.deb
-----> Writing profile script
-----> Rewrite package-config files
-----> Node.js app detected
-----> Creating runtime environment
       
       NPM_CONFIG_LOGLEVEL=error
       NPM_CONFIG_PRODUCTION=true
       NODE_VERBOSE=false
       NODE_ENV=production
       NODE_MODULES_CACHE=true
-----> Installing binaries
       engines.node (package.json):  7.7.1
       engines.npm (package.json):   unspecified (use default)
       engines.yarn (package.json):  unspecified (use default)
       
       Resolving node version 7.7.1...
       Downloading and installing node 7.7.1...
       Using default npm version: 4.1.2
       Resolving yarn version (latest)...
       Downloading and installing yarn (0.28.1)...
       Installed yarn 0.28.1
-----> Restoring cache
       Skipping cache restore (not-found)
-----> Building dependencies
       Installing node modules (yarn.lock)
       yarn install v0.28.1
       [1/4] Resolving packages...
       error Your lockfile needs to be updated, but yarn was run with `--frozen-lockfile`.
       info Visit https://yarnpkg.com/en/docs/cli/install for documentation about this command.
-----> Build failed
 !     Outdated Yarn lockfile
       Your application contains a Yarn lockfile (yarn.lock) which does not
       match the dependencies in package.json. This can happen if you use npm
       to install or update a dependency instead of Yarn.
       Please run the following command in your application directory and check
       in the new yarn.lock file:
       $ yarn install
       $ git add yarn.lock
       $ git commit -m "Updated Yarn lockfile"
       $ git push heroku master
    
       https://kb.heroku.com/why-is-my-node-js-build-failing-because-of-an-outdated-yarn-lockfile
 !     Push rejected, failed to compile Node.js app.
 !     Push failed```

[ghost]

Link in #457 worked

[michielbdejong]

Renamed it to the part that's not in #457