Support --compilers arg

[vidbina]

In order to support mocha compilers, the CLI --compilers argument has been pulled to the electron-mocha front-end, which makes calls like electron-mocha --compilers js:babel/register test/example.js possible in case one has written tests in ES6 for example.

[jprichardson]

Why not just use require? Also, ping @jg123 for his thoughts (re: #15)

[vidbina]

Hey @jprichardson what do you mean with the require? I basically just mimicked mochajs/mocha/bin/_mocha. I noticed that a considerable part of the code in electron-mocha was about providing a custom implementation of mochajs/mocha/bin/_mocha so in the spirit of pragmatism I came up with the simplest way out. If not "sound", I'd be glad to receive proposals for a fix 😉

[jprichardson]

If you create a file, say babel.js that includes require('babel-core/register'), you could then call electron-mocha --require ./babel.js test-file.js.

But I imagine that a lot of people are going to expect the Mocha --compilers flag to work, so maybe I'll just accept this since it's not much code to maintain.

[vidbina]

Ah. I haven't tried that approach before, but I guess both options will do. Personally I'd prefer the --compilers approach because it:

• is the proposed implementation posted on babeljs.io/docs/setup#mocha for Mocha tests (which means many are familiar with it and offering a similar usage pattern makes life easier for most)
• does not involve an additional file to be required which only contains some boilerplate. The --compile flag performs the require(mod) and appends to extensions. The one thing it doesn't do is set up watchers as Mocha does, but I guess for now we'll take that as a minor inconvenience.

[jg123]

I also prefer not having to create the extra file. What perfect timing!

[jprichardson]

Decided to merge because I anticipate demand will be high for this feature. Thanks for your contribution.