Rename cindex file to match python location

Also delete the binary file that was mistakenly added
to git.

Signed-off-by: Jonas Kalderstam <jonas@kalderstam.se>
Pass arguments to pytest; Plot tests skippable

Added ability to pass command line arguments to pytest.
In addition, I marked tests which do plotting as 'plottest'.
This combination allows the following invocation:

    python -m lifelines.tests -m "not plottest"

Which will skip plotting tests. Any arguments that pytests
accepts can be passed now.

Signed-off-by: Jonas Kalderstam <jonas@kalderstam.se>