Improve Canvas constructor (see issue #79)
Update tests to go with new Canvas
Flake8 stuff

I need flake8 integrated in my IDE :/
Use create_native flag in tests. This is where the API was weird.
Add flake cmd to python make module and rem nosetests script.

Easily test style using flake8
Instead of nosetests, use ``make test`` ``python make test``.
Remove double colon in numpy-ish doctrings.
Merge pull request #88 from vispy/better-canvas-api

Improve Canvas constructor (see issue #79)