Revert "Remove unused sprockets-helpers dependency"
Revert "Remove unused sprockets-helpers dependency"

Guess we do need it...

This reverts commit 5edc902c47efc7b00c016216017d52a035fcc330.

middleman/middleman-sprockets,williamcoates/middleman-sprockets,middleman/middleman-sprockets,williamcoates/middleman-sprockets,ryanmark/middleman-sprockets,middleman/middleman-sprockets,williamcoates/middleman-sprockets,ryanmark/middleman-sprockets,ryanmark/middleman-sprockets