feat(scrollfix): Added uiScrollfixTarget

Add the ability to specify a target container to moniter for scroll
events instead of $window
fix(scrollfix): Removed jquery dependency

Fixes #14
fix(scrollfix): $window must be wrapped in angular.element()
Merge branch 'scrollfix'

* scrollfix:
  fix(scrollfix): $window must be wrapped in angular.element()
  fix(scrollfix): Removed jquery dependency
  feat(scrollfix): Added uiScrollfixTarget