Replace helpers with extensions

Replaces the helpers to real extensions, so they don't rely on de helper
files, imho a bit cleaner. Will also make for a cleaner config.
Added a LegacyFacade extensions for 0.5.
Fix tests
Merged in latest from 0.6
Cleaned up
Fix broken HTML extension
And fix the URL extension :(
Allow us to alter behaviour for testing
Fully test Laravel extensions
Fix code style
Merged in 0.6-extensions. Fix #97, fix #99, fix #68