feat: Add support for yaml configuration file

[furudean]

I added support for .yml and .yaml config files as per request in #892.

I wasn't sure how to implement tests for this, so suggestions are welcome.

[coveralls]

Coverage increased (+0.02%) to 96.667% when pulling 362eff0 on c-bandy:master into d7a9d6a on istanbuljs:master.

[JaKXz]

@c-bandy thank you for the PR! would you mind adding to the README where it mentions the different kinds of rc files you can have?

[coreyfarrell]

I would like to see some basic tests for this. To do so please:

1. Add js-yaml as a dev dependency.
2. See test/nyc-integration.js at about line 445 (search for describe('.nycrc', function () {). This is where we have testing for .nycrc. I think we should have similar tests for js-yaml.

[coreyfarrell]

Just a couple minor coverage related issues then this should be good to merge.

[coreyfarrell]

@c-bandy Also please mention these new configuration files in our README.md. See https://github.com/istanbuljs/nyc#configuring-nyc

[furudean]

@coreyfarrell Added! 👍

[bcoe]

if we are going to support multiple yaml parsers, let's pull the logic for loading the yaml parser into its own module lib/yaml ...

I'd rather just support one yaml parser. We're opening ourselves up to config bugs that exist in one parser but not the other, I'd rather be less democratic and pick one.

[bcoe]

@c-bandy really appreciate this contribution 😄 the tests certainly seem like they're on the right track.

[bcoe]

@c-bandy I missed that both yaml parsers are optional (hadn't noticed js-yaml was a developer dependency); I'm more open to checking for both 👍still might be nice to encapsulate the logic that checks for yaml parsers into a lib/yaml.js parser ... would be neat to potentially consider adding a similar toml.js parser as a follow on.

[furudean]

@bcoe Thanks for your feedback! I will look into making these changes today

[coreyfarrell]

@c-bandy please hold off for a bit, we've been having a discussion on our slack about the best way to handle yaml and other formats. I don't think we've come to a consensus yet. At this point we are focused on getting nyc@14.0.0 released. YAML config will be a non-breaking change so we can consider it for 14.1.0.

[isaacs]

Copying here my suggestion from the discussion elsewhere: since so many testing libraries include js-yaml anyway, it's probably best to just declare that one as a dep and use it.

[bcoe]

@c-bandy sorry to be a pain, I know it's annoying when a PR is blocked by folks not being able to reach consensus. If you'd like to join in with the conversation, we actually have a slack here:

http://devtoolscommunity.herokuapp.com/

Would love to get your opinion as we opine.

[furudean]

I have incorporated changed based on our discussions

[bcoe]

this is looking good to me, I like the introduction of the lookup table.

[coreyfarrell]

I'm approving this but not sure it should be merged right now or wait until 14.0.0 is released.