Bug Fixes, Various Error Handling Improvements

PR's included in the milestone can be found here: https://github.com/channelcat/sanic/milestone/1?closed=1

Changes:

• Addition of Python 3.6 to tox tests and travis tests (We will eventually be using the tox.ini as our main travis testing script as well)
• New raising of error if an invalid response is returned
• Add in a way to encode objects that are un-encodable in response objects