Tests

Moved tests dir from packge dir to project dir.
Moved test_runner to project dir.

Changed test_runner to run tests in python2 and python3, in that order.
Changed imports in tests to point to the correct paths.
Build and setup

Changed setup.py to use `setuptools` instead of `distribute`.
Changed .gitignore to ignore the files and folder generated by build_egg script.

Added `build_egg` script to build egg for python 2 and 3, in that order.
Imports

Changed imports to relative ones, so it is more compatible to python 2.