bin support

[vdegenne]

Could you review this PR and consider it to be interesting.
I just added a bin file and the bin property in the package.json file.
So when the package is installed globally npm i -g get-port one can actually type the following in the system terminal :

get-port for any available port
get-port 3000 3020 for the preferred ports
get-port -r 3000,3100 for the range

I found it useful for myself to check if a port is available before using it in my application or sometimes even I just want the system to choose a port that I'll be using fixed throughout my project.

If you think that is interesting, please accept the PR and I let you change the readme to introduce this feature.

[vdegenne]

I fixed the bin file to agree with the es-lint rules, there is a last failing rule however, that I can't fix.
It seems to be a bug : mysticatea/eslint-plugin-node#126
But I tested locally and the bin support is working fine.

[sindresorhus]

There's already a CLI, just in a separate package: https://github.com/sindresorhus/get-port-cli PR welcome there if there's anything missing.

[vdegenne]

Oh I didn't know.
What is the motivation behind separating both the API and the CLI by the way ?
Given that both the API and the CLI are very small in size, it would have been great to bundle the both together, just my opinion.

[sindresorhus]

sindresorhus/ama#17