Add a mode to docgen to run the code samples in the documentation.

This alleviates copying them elsewhere to ensure they are not broken.
Merge pull request #2078 from abergeron/doc

Add a mode to docgen to run the code samples in the documentation.
Fix test in fast_compile
fix test in FAST_COMPILE mode.
Fix test in FAST_COMPILE mode
pep8
Merge pull request #2164 from nouiz/tests

Fix buildbot errors.
Add pseudo-math in the docstring for GemvSS and OuterSS.
Merge pull request #2167 from abergeron/blocksparse_doc

Add pseudo-math in the docstring for GemvSS and OuterSS.
Closes #2141