Update port to OS X

[larryhastings]

I just redid all the platform abstraction stuff. I tried to keep the Mac stuff working but I might have broken it. Please download fix and send me a pull request!

[zitterbewegung]

Hi I believed I addressed this with pull request #27 . The to_nano variable wasn't renamed to the proper name preventing the build. I attempted to run the unit tests and I was wondering how many should pass? According to your talk at PyCon at least a simple fibonacci program should pass and below is the correct output on my build.

Python 3.6.0a0 (default, Jun  5 2016, 21:43:29) 
[GCC 4.2.1 Compatible Apple LLVM 7.3.0 (clang-703.0.31)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> def fib(n):
...     if n < 2: return 1
...     return fib(n-1) + fib(n-2)
... 
>>> fib(10)
89
>>>