fix failing tests

[jakoch]

The tests are currently failing (see https://travis-ci.org/jakoch/PHPTracRPC/jobs/114876495#L190), because they were written as live tests against a Trac endpoint (which is now out-of-service) and not as mocks.

Todo

• [ ] rewrite tests using mocks
• [x] or find another trac endpoint for testing
  • switched to https://josm.openstreetmap.de/rpc

[jakoch]

I've added some tests with this commit https://github.com/jakoch/PHPTracRPC/commit/6e8c2c907f16dc90968876bdca867c1172806e23 - - 45% coverage