Clean browser before karma

[lucasfcosta]

Hi @keithamus, according to what we've been talking on #515, this is the Makefile I was using when making my changes. I avoided using lib/** as you said, instead I added the clean-browser task as a dependency of every browser's tests.

I've also edited CONTRIBUTING.md with clearer instructions according to the new Makefile.

I also have a doubt: are you guys planning on using Gulp? Personally, I think it would be more friendly both for different platforms (Windows doesn't have Make available, for example) and for JS programmers (which are used to this kind of task automation).

[keithamus]

Thanks for this @lucasfcosta 😄. I hope to get some time over the holidays to do some refactoring in a 5.x.x branch and will probably take a look at the build tasks at the same time. I'm not exactly the biggest fan of Gulp et al but I'd like to move to npm scripts for straightforwardness and windows compatibility.

[lucasfcosta]

Ah, sure, I totally understand your point of view and it seems very reasonable.
If you need any help with these things you can count on me!

Thank you too!