accepted differences in post_id in new patterns
added comments on bridge_api failing tests now that there is less differences
corrected patterns for database_api (one test also changed to fit interface of fat node - completely stopped working for new HiveMind due to API difference)

- Added xfail mark to failing tests

- Added pattern validator
- Added patterns for 5000000 blocks
- Added bridge_api pattern tests - failing tests are marked with XFAIL
- Added marks to all tests

- Response validator has been added: it validates if error or result
  fields are present in response. Occurence of error field will fail
  the given test.
- In order for validator to work a path to test directory must be added
  to PYTHONPATH i.e you can run py.test from inside of tavern dir using:
  PYTHONPATH=$PYTHONPATH:$(pwd) py.test -v

- Initial implementation of tests with tavern freamework
- All tests are green atm because only thing that is checked is
  response_conde
- More works on tests in next commits