Added Messages instance for list of Message's
Added AlexHelper module
Added class of messages representing lexical errors.
Changed signature of span
Changed signature of actions and token action.
Changed signature of error action
Changed signature slightly
Exported MonadPositions
Made token handle monadic token creators
Modified AlexHelper, renamed to AlexWrapper
Renamed mkToken, moved out of class
Slight change to Show instance
Added no-context variants
Added Context monad
Added example lexer
Deleted SourceLoader, added SourceBuffer
Added new modules
Changed usage of ByteString
Corrected import and instances.