And remove coveralls because it is indeed broken

.travis.yml

@@ -7,5 +7,4 @@ python:
   - "3.4"
   - "3.5"
 
-script: python setup.py test --cov metrik
+script: python setup.py test
-after_success: coveralls

setup.py

@@ -12,10 +12,9 @@ setup(
         'luigi >= 2.2.0'
     ],
     setup_requires=[
-        'pytest_runner'
+        'pytest_runner >= 2.9'
     ],
     tests_require=[
-        'pytest',
+        'pytest >= 2.9.2'
-        'python-coveralls'
     ]
 )