Adding backwards compatibility with sprockets 3 and sprocket-rails 2
Adding backwards compatibility with sprockets 3 and sprocket-rails 2

This should make @alexkravets work fix the issues pointed by @jfirebaugh
in https://github.com/jfirebaugh/konacha/pull/219.
Simply specify conditionals around sprocket-rails 3 (instead of
sprockets 3) since the breaking changes come from sprocket-rails.
Also, early versions of sprocket-rails 2 didn't have VERSION and didn't
require it properly
(https://github.com/rails/sprockets-rails/issues/131).

jfirebaugh/konacha,jfirebaugh/konacha,jfirebaugh/konacha