Added top level convert class, updated init.py to load v#s
Notebook version conversions done right?
Fixes (iptest), simplified v1, v2, .. , vX import code
Relative import (suggested by @MinRK)
Revert b23f5b1525e76d5a
Relative import
Some small fixes and changes of nb version conversion
Small fix
Added nbformat ver conv tests, fixed some bugs
Added test nbs to setup and removed todo
Don't reset the readline completer after each prompt

This makes it impossible to setup a custom completer. The comment says that
"we must ensure that our completer is back in place," but I don't see why. All
that does it make it impossible to use a different completer. One can trick
IPython into not doing this by monkeypatching ip.has_readline to False, but
then certain features like multiline editing are no longer enabled.

See https://github.com/davidhalter/jedi/pull/321.
Spelling/typos fixes
Updated JSON error message to limit full error to 80 characters.
Also added a comment to explain why.
make default language highlight configurable for html
javascript is no place to start adding title tags
added descriptions which were deleted from JS
add more tooltips for Cell menu
Kernel and Help menu tooltips
tooltips for View and Insert menus
added some tooltips for the File menu