Some fixes and improvements

What's done:

• #20 issue fixed. Now cakes unbaked remain unbaked with no errors
• #22 documentation (readthedocs) added (sorry for english, guys, I'm working on it)
• #23 small readme updates. Big thanks to @xfenix
• #24 explicit tox dependencies to avoid unexpected surprises
• #25 working with piece of cake as well as with cakes
• #26 hand made any object, not just cakes. Under the hood objects are wrapped into cakes. Thanks @legatusAlex for inspiration and reviews
• Some minor bugs/details fixes