DOC/BUG: Move docs from __init__ to class

If documentation is included in the __init__ method, it is not rendered
by sphinx and is in turn not available anywhere. Moving it over to the
class declaration makes it appear in the class' index.
DOC: Remove Returns section

I'm tired of these annoying comments:

(╯°□°）╯︵ ┻━┻
Merge pull request #311 from ElDeveloper/init-docs

DOC/BUG: Move docs from __init__ to class