Fix packaging issues

In svg.py import geometry using relative import;
Rename svg.test.py to svg_test.py as dots bug Python sometimes...;
testsuite.py import the package, not the module (nose finds its way
with packages, better than me)

Launching `nosetests` run all the tests in testsuite.py + svg_test.py.

To run svg_test.py, cd to ../ and run python -m svg.svg_test [args]

Those modifications come from this StackOverflow question of mine:
http://stackoverflow.com/q/20959811/976723