Improve parity with ptpython and ptipython's entry points
Improve parity with ptpython and ptipython's entry points

* Run user config. Close #16
* Pass startup_paths
* Pass history_filename

Much of this was copied from
ptpython/entry_points/run_ptpython.py and
ptpython/entry_points/run_ptipython.py.

sloria/konch