Add CommonJS support in accordance w/ Angular convention

[bendrucker]

Implements #566

[coveralls]

Coverage remained the same at 92.85% when pulling 718c375 on bendrucker:cjs into db222d0 on firebase:master.

[katowulf]

Thanks, Ben! Let me find some time to review and see if we can get this in 1.0

[jamestalmage]

IMO, this is a no brainer. It is now the official way angular exports modules for CommonJS consumption. The sooner I can stop shimming these, the better.

[jwngr]

I think we should also list index.js in the files list right here. It may not be required since npm may automatically include the file listed in main, but I'd prefer to see it listed in files as well.

[jwngr]

Yeah, I mean this looks like goodness to me. I made one comment which I'd like to see addressed but then I'm a thumbs up on merging this in.

[jwngr]

Actually, now that I think about it, I'm not sure this is compatible with the fact that we got rid of $firebase in favor of three separate services, $firebaseArray, $firebaseObject, and $firebaseAuth, all of which can be injected invidually. @bendrucker, I'm not sure how that fits into the string we are exporting here.

[jwngr]

Ignore my last comment; not thinking properly today. The module is still called firebase, so we are all good.

[bendrucker]

Totally right on the need to include it in files. That's done. And per your comment and correction, that's exactly right. It only has to do with the module name, not any of the injectables.

This requires much less of a hack and dries up your modules when you do build with Browserify.

Here's ES5: https://github.com/bendrucker/angular-stripe/blob/f93a874097b30c757410ac5d5050a020edc01590/src/index.js

And ES6: https://github.com/bendrucker/angular-countdown/blob/bd5555d2302204f8e8874d78d95c4a9b3879a683/src/index.js

[coveralls]

Coverage remained the same at 92.85% when pulling 30861bd on bendrucker:cjs into db222d0 on firebase:master.

[katowulf]

Looks good, Ben. Thanks.