* Add content_type flag to Sanic.static
Fixes#1266
* Fix flake8 error in travis
Add line to document `content_type` arg
* Fix content_type for file streams
Update tests
herp derp
* Remove content_type as an arg to HTTPResponse
`response.HTTPResponse` will default to `headers['Content-Type']` instead of `content_type`
https://github.com/channelcat/sanic/pull/1267#discussion_r204190913
