Change handling of f_conv argument to cosmicray_lacosmic

This change fixes a sphinx build error
White space/typo cleanup in documentation
Make travis doc build fail if there are warnings
Move install.rst to docs/ccdproc and fix formatting error
Add install.rst to a toctree
Add link in README to install docs

and do some basic reformatting....
Start revised cosmicray docs
Rename create_variance to create_deviation
Merge pull request #150 from mwcraig/loose-ends

Wraps up a few remaining loose ends before 0.1.1