ipython changes to fix notebook export. fixes #162

IPython was broken as `mistune` got updated to `0.5`.
JuliaBox IPython fork fixed (https://github.com/tanmaykm/ipython/commit/5e95f88987c015ef2881716c7243c0a2127112ea) and docker build updated.

Could not move to current IPython dev branch as notebook upgrade doesn't seem to be working fine yet,
and upgraded JuliaBox notebooks won't open on the IPython released version (which will be the
most common version installed by users locally).