Choose LICENSE for gulp-bem orgainzation

[Yeti-or]

@blond @zxqfox do we need to force MPL-2.0 here too, or this is not so important?

[blond]

@tadatuta?

[tadatuta]

I don't see any reason not to use MPL-2.0 in any of our repos.

[qfox]

Can we use package.json-fields to describe authority and licenses instead of putting LICENSE-file in each repo since package.json has license field?

[Yeti-or]

@zxqfox and don't forget about README =)