TravisCI: Removed /dev/null redirection

Travis is folding the commands now automatically :)
Merge pull request #24 from Turbo87/travis

TravisCI: Removed /dev/null redirection
TravicCI: Install coverage dependency in after_script section

We don't need this to run the tests and the results will be visible a
bit faster now.
TravisCI: Moved psql -U to the front
TravisCI: Added comments
TravisCI: Enabled raster support
TravisCI: Install PostGIS 2.x via CREATE EXTENSION
Merge pull request #26 from Turbo87/travis

TravisCI: Use "CREATE EXTENSION" to install PostGIS 2.x
Merge pull request #23 from Turbo87/docs-styling

Improved docs styling
doc: Fixed webfonts link

The http:// was giving troubles on HTTPS servers like readthedocs.org