ChatterBot 0.4

This is a fairly major release with many changes breaking backwards compatibility.

Introducing Input & Output adapters

IO adapters have been divided into two new modules (input adapters and output adapters).
This change makes it possible to write less code by being able to mix and match different
types of inputs with different types of outputs.

Improved documentation

Lots of new documentation has been added. Check it out! http://chatterbot.readthedocs.io/

Other changes

• Removed the weather adapter [https://github.com/gunthercox/ChatterBot/commit/8856bce1fad2ae387e4bfc5eccd7ac256f4b0081]
• Added output adapter for the Mailgun api [https://github.com/gunthercox/ChatterBot/commit/4e9ef44f1fc1db32e2bdcaa67073068979813df0]
• Renamed EvaluateMathematically logic adapter to MathematicalEvaluation [https://github.com/gunthercox/ChatterBot/commit/d62771b0777580fa05d69c125c042b7590dbbae3]
• Removed optional logic_adapter parameter. Only logic_adapters is now allowed.