Pull request of "Testing models" Trello card

These are the tasks done:
- Setup Travis and Coveralls
- User creation
- Schema creation
- Node type properties creation, edition and deletion for each possible type
- Relationship type properties creation, edition and deletion for each possible type
- Relationship creation, edition and deletion
- Account creation, edition and deletion
- Node media link creation, edition and deletion

The original files that have been modified are:
- README.srt -> Badges added
- sylva/graphs/tests.py -> All the file is new, because the old contets was really old