HTML Formatter
Updated 'Help Formatter' feature

Added html in the list of available formatters (fixes Travis builds)
Use lxml for pretty output
Output also feature description (if available)
Output also scenario description (if available)
Added some tests
Handle undefined locations correctly
Handle several parameters correctly
Moar html formatter tests
Add lxml as dependency for travis builds
Collections is not available in py26, use our own class
Move Counter class in behave/compat/collections