reqs.txt -> requirements.txt
Bump required numpy version so it works on OS X
Move tests out of installed package
update setup.py
Fix installation
Export zss.compare.distance to zss.compare
Move tests.test_tree to zss.simple_tree
Fix example
Moved tests --> zss/tests

I prefer my tests dir to be inside the package. It will only get install
if you tell setup.py to install it.

Signed-off-by: Tim Henderson <tim.tadh@gmail.com>