[fix #2] Made team system.

* worked on team system
* added teams, started working on invites
* added travis yml
* fixed travis config, added simplecov, covered user model
* Added travis status image
* Fixed database config for travis
* Added gem sqlite3 for travis
* added migrate run
* covered models and controllers but omniauth callbacks left
* fixed existant -> existent
* moved skipped authenticated tests to integration
* covered omniauth callbacks controller in integration
* added invite mailer, added coveralls
* moved to minitest + capybara
* added invite and leave features
* added form for team edit
* added button to add new team, fixed duplication of mates
* added foreman, simplecov html formatter
* added ability to transfer ownership
* added hub gem to gemfile