FIX: Nest freetype imports
Misc small tweaks and fixes.

* Updated readme to stick to 70 chars linewidth. Also minor
  changes to allow copy-pasting it into the index.rst for website.
* Make imshow not get stuck on building gallery
* Gallery building use Canvas context manager.
flake
Merge pull request #465 from almarklein/misc-tweaks

Misc small tweaks and fixes.
Merge pull request #466 from almarklein/misc-tweaks

flake remaining from #465
Delay program validation until Texture units are asigned.

Hopefully this fixes #459. Also see #458.
Merge pull request #467 from almarklein/delay-program-validation

Delay program validation until Texture units are asigned.
Changed README from markdown to rest.
Merge pull request #469 from rossant/readme-rest

Changed README from Markdown to ReST
Merge pull request #463 from Eric89GXL/fix-ft

FIX: Nest freetype imports
ENH: Allow set_viewport to take tuple
Removed old SVG files.
Updated Vispy module's docstring.
Added references in the doc index.
Added more doc in index.rst.
Merge pull request #476 from rossant/improve-doc

Adding a bit more information in the documentation
Merge pull request #473 from Eric89GXL/viewport

ENH: Allow set_viewport to take tuple