NF: write __config__.py with compile variables

Write the discovered compile-time variables into a file
``dipy/__config__.py`` so dipy code can act depending on the result of
the compile - for example compile-time presence of openmp.
TEST: compare against different energy profile with SSE2
Export build flags to __config__.py
TEST: use exported build flags to select oracle energy profile
TEST: skip regression tests when SSE2 is not supported
BF: apparently, 'has_key(...)' was removed from dict in python3
Generate the config file earlier
HACK: generate __config__ module as a cython extension to make sure it is generated before it is moved to the module install directory
Remove __config__.pyx, will be auto-generated
Using simpler __setup__.py, suggested by Matthew
Remove DipyConfig and build_flags classes
PEP8: remove extra empty lines and set maximum line length to 80 characters
Merge pull request #489 from omarocegueda/fix_profiles

Fix diffeomorphic registration test failures