Added instance for Maybe.
Updated tests.
The instance for Maybe can now parse the string "Nothing".

"Nothing" -> Nothing :: Maybe a
"Just Nothing" -> Just "Nothing" :: Maybe Text
Type `Maybe (Maybe a)` can not be parsed in the route file but it is safe to assume that :
"Just Nothing" -> Just Nothing :: Maybe (Maybe a)"
and that
"Just Just Nothing" -> Just (Just "Nothing") :: Maybe (Maybe Text)
Fixed missing imports..
Fixed. Take 2.
Streamlined `fromPathPiece` implementation.
Fixed erroneous behavior when parsing faulty inputs.
Merge github.com:MomemtumMori/path-pieces

Conflicts:
	Web/PathPieces.hs