Implement >>
Fix >> :facepalm:
Replace if and nots with if-not
Add  test doc for reproduce the stack overflow.
Add script for build dev docs.
Version number change on doc.
Update readme.
Start doc refactoring.
Reorganize some sections and add empty sections.
Make mlet macro non recursive.
Update changelog.
Make nil as instance of maybe monad and works like nothing.

Just for avoid accidental null pointer exceptions.
maybe? function now returns true with nil as parameter.

And add additional tests for it.
Merge pull request #9 from niwibe/nil-as-nothing

Make nil as instance of maybe monad and works like nothing.
Add default constructor for identity type.
Update changelog.
Remove requirements section from cats docs.
better user.test
WIP
Make >=> and <=< context-aware