Re #8351. Append a space to the string representation.

This is to get around a bug in IPython 1.1. The space is added to the
representation only on the python side, not the C++ side.
I believe this will have minimal/zero real impact and avoids crashing
the IPython console.
Re #8351. Amend tests to account for the additional space.
Merge remote-tracking branch 'origin/bugfix/8351_ipython_datetime_error'