Support ptipython

[tkf]

I thought ptypthon may fix segmentation fault issue since it uses prompt_toolkit (#7 (comment)).

It didn't work, though:

julia> using IPython; IPython._start_ipython(:customized_ptipython)   
                                                                      
Python 3.5.2 |Continuum Analytics, Inc.| (default, Jul  2 2016, 17:53:06) 
Type 'copyright', 'credits' or 'license' for more information
IPython 6.4.0 -- An enhanced Interactive Python. Type '?' for help.
                                                             
In [1]: sin = Main.sin

In [2]: s

signal (11): Segmentation fault
while loading no file, in expression starting on line 0
zsh: segmentation fault (core dumped)  julia

Still, it makes sense to support Python REPLs other than IPython?

[coveralls]

Pull Request Test Coverage Report for Build 52

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 78.571%

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Totals
Change from base Build 47:	0.0%
Covered Lines:	66
Relevant Lines:	84

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💛 - Coveralls