#3 Percent and Question mark symbols in comments in notebooks get modified on conversion to py

[Fergal Mullally]

The fix in #2 created a new problem of text in comments getting modified

Ipython magic commands (%) and (?) in notebooks are now commented
out in the conversion to py, and restored on conversion to notebooks.

However, similar symbols in comments now become garbled, something I still
have to fix. magic.ipynb gives some examples