Fixes #2

Looks like IPShellEmbed(user_ns=locals) with default 'argv' value 'None' works good if:

1. You are on a bare shell
or
2. You have set 'classic 1' at ipythonrc

but not when interacting with a doctest.

I dont know why, but setting 'argv=[]' solves this issue AND honor user preferences. Maybe its a IPython bug, but working around here does not harm anyone.