Fix import of compiled module with python3.

This at least fix #331
Add test pyc

Should succeed for python2 and faild for python3
Fix pyc test for python3

To import pyc modules, we must move them out of the __pycache__
directory and rename them to remove ".cpython-%s%d".

This should still faild with python3 (UnicodeDecodeError)
Fix read mode for pyc files

Now all test should pass on travis.
Move dummy pyc to dummy package
Add compiled modules sources + readme
Add test_compiled

Should pass on travis since there is no precompiled modules yet
Change sys.path for the test to succeed.

Tested locally with a python3 extension module (in
/extensions/compiled33).

Also tested that reverting a75773cf9f7a9fde2a7b2c77b9846b4f0dd5b711 make
the test fail.
Move extensions dir into test
Add precompiled extension modules
Merge pull request #375 from ColinDuquesnoy/dev

Fix import of compiled module with python3.