sprockets-rails 3.x requires sprockets 3.x
Merge branch 'master' into beta-only
Drop old sprockets versions
Merge branch 'master' into beta-only

Conflicts:
	.travis.yml
Merge branch 'master' into beta-only
Merge pull request #184 from rails/beta-only

sprockets-rails 3.x will only support sprockets 3.x