Fix tests

With this list of gems, all tests failed:
```
$ bundle list
Gems included by the bundle:
  * activesupport (4.2.0)
  * bundler (1.7.9)
  * diff-lcs (1.2.5)
  * dilicom_api (0.0.5)
  * faraday (0.9.0)
  * faraday_middleware (0.9.1)
  * faraday_simulation (0.0.2)
  * gem-release (0.7.3)
  * i18n (0.7.0)
  * json (1.8.1)
  * minitest (5.5.0)
  * multipart-post (2.0.0)
  * rake (10.4.2)
  * rspec (3.1.0)
  * rspec-core (3.1.7)
  * rspec-expectations (3.1.2)
  * rspec-mocks (3.1.3)
  * rspec-support (3.1.2)
  * thread_safe (0.3.4)
  * tzinfo (1.2.2)
```

After:
![capture d ecran 2014-12-24 a 10 32 11](https://cloud.githubusercontent.com/assets/411619/5547353/89545972-8b58-11e4-912d-55c236dc7100.png)