Localizations according to flask.ext.babel standard mechanism
locales validation and remove duplication of en_US in settings
Check for default language corruption
commented code deleted
Explicit Babel defaults removed
Fix path for babel

babel.cfg was not updated when we moved flask_version
Merge pull request #262 from kcrisman/master

Fix path for babel
Make init.sage work

Ideally, this would later be changed to use `attach` again.
Fix various sage import locations
Create nodoctest.py

This should fix the doctest errors in sagenb, as well as give a tiny bit of info to anyone seeking to use Grinder with sagenb.
Merge pull request #280 from jdemeyer/fix_imports

Fix various sage import locations
Disallow spellcheck in code cells
Cache bust canvas3d so they reload properly
Document toggle between source code and doc

It was not clear before that it is a feature, not a bug, that after e.g.
`factorial?[tab]` if you tab again you get source code.  This is actually quite useful.
Merge pull request #283 from kcrisman/spellcheck

Disallow spellcheck in code cells
Use atomic_write() to have no corruption in case of crashes
Merge pull request #285 from kcrisman/togglesource

Document toggle between source code and doc
Fixes #275
Add doctest for pull request #287
Make fixed format Fortran work in sagenb
Allow OSError