DDL: Switched column filtering

The double negative for creating the gis_cols was confusing and is
easier readable like this.
DDL: Fixed indent

PEP8 complained
DDL: Added more comments
Merge pull request #17 from Turbo87/ddl

Improved __init__.py readability
Added TravisCI config file
Merge pull request #19 from Turbo87/travis

Added TravisCI support
TravisCI: Mute setup commands

We only care about the test and converage output for now
TravisCI: Test with Python 3.3 too
TravisCI: Added POSTGIS_VERSION environment variable
TravisCI: Only send notification mails on status change
TravisCI: Added PostGIS 2.0 build option

Travis should now test on both 1.5 and 2.0.3
README: Added TravisCI build status image
Merge pull request #20 from Turbo87/pg2.0

Added PostGIS 2.0 support to TravisCI
setup.py: Disable shapely dependency on Python 3.0 and above
test_shape: Skip tests if the shapely import fails

This will skip the shapely-related tests on Python 3
test_elements: Explicitly pass byte strings to WKBElement
Merge pull request #21 from Turbo87/py3.3

Added Python 3.3 support for TravisCI