setup.py: Fixed formatting
setup.py: Moved test package dependencies to requirements.txt
Replaced nose by py.test

nose.tools is still used in some test though. cleanup will follow.
tests: Removed nose.tools usage
Removed obsolete setup.cfg

We don't need the nosetests config anymore
setup.py: Removed obsolete test_suite attribute
tests: Moved to tests to root folder

They are more visible here and shouldn't be part of the geoalchemy2
package itself
tests: Merged duplicate imports and moved to the top
tests: Removed unittest.TestCase inheritance
tests: Use pytest fixtures where possible
Merge pull request #72 from Turbo87/pytest

Replaced nosetests by pytest