Also:
* Added a ``--no-startup`` option to disable this behavior. Previous
logic to try to execute the code in charge of this funcionality was
flawed (it only tried to do so if the user asked for ipython/bpython
and they weren't found)
* Expand ``~`` in PYTHONSTARTUP value.
Thanks hekevintran at gmail dot com for the report and initial patch.
Refs #3381.