Add Travis CI configuration.
Merge pull request #228 from toggl/roosmaa-travis

Add Travis CI configuration.
Remove unused ValidationContext class.
Register ITimeProvider for tests.
Add testing configuration to solution.
Add new data and json objects.
Add data<->json object convertors.
Add data store interface and tests.
Make primary key auto increment.
Add SQLiteDataStore implementation.
Add query builder to SQLiteDataStore.
Add messaging about data changes.
Add new model implementations.
Move temp database creation to base Test class.
Add empty model test fixtures.
Verify model property names.
Verify model constructors.
Test property changed event firing.
Generate property changed event for foreign model instance replacement.
Test model relations.