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
Spelling/typos fixes
Updated JSON error message to limit full error to 80 characters.
Also added a comment to explain why.
Merge pull request #4198 from jdfreder/versionconversion_nbconvert

add upgrade / downgrade to nbformat