Properly mark format strings as unicode

Signed-off-by: Michal Čihař <michal@cihar.com>
Better way to concatenate parts

Signed-off-by: Michal Čihař <michal@cihar.com>
Run pylint during build

Signed-off-by: Michal Čihař <michal@cihar.com>
Use py.test to run tests

Signed-off-by: Michal Čihař <michal@cihar.com>