Remove unnecessary includes, add ARCHFLAGS env variable

[oxtopus]

This builds for me on my laptop, but only if I specify ARCHFLAGS="-arch x86_64" otherwise, "-arch x86_64 -arch i386" is passed which causes errors.

[oxtopus]

Though it builds, I do get errors in the unit tests:

============================================================================== test session starts ===============================================================================
platform darwin -- Python 2.7.5 -- pytest-2.4.2 -- /usr/bin/python
plugins: cov, xdist
collecting 216 items / 1 errors
===================================================================================== ERRORS =====================================================================================
____________________________________________________________ ERROR collecting tests/unit/nupic/engine/network_test.py ____________________________________________________________
tests/unit/nupic/engine/network_test.py:27: in <module>
    from nupic import engine
nupic/engine/__init__.py:26: in <module>
    import nupic.bindings.engine_internal as engine
nupic/bindings/engine_internal.py:28: in <module>
    _engine_internal = swig_import_helper()
nupic/bindings/engine_internal.py:24: in swig_import_helper
    _mod = imp.load_module('_engine_internal', fp, pathname, description)
E   ImportError: dlopen(/Users/amarshall/nta/nupic/nupic/bindings/_engine_internal.so, 2): Symbol not found: __ZNSt8ios_base4InitD1Ev
E     Referenced from: /Users/amarshall/nta/nupic/nupic/bindings/_engine_internal.so
E     Expected in: flat namespace
E    in /Users/amarshall/nta/nupic/nupic/bindings/_engine_internal.so
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: stopping after 1 failures !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
============================================================================ 1 error in 0.73 seconds =============================================================================

[rhyolight]

👍 We'll figure out the arch flags thing. Needs at # TODO maybe.

[david-ragazzi]

Symbol not found: __ZNSt8ios_base4InitD1Ev

This error is because some static library was not linked to engine_internal.so and so the symbol is not found. Believe me, I spent some time to figure that I should use extra_objetcts parameter to pass the static libraries.