Remove duplicate dependency

Joe Paul · Joe Paul · commit a9eb8d36541b · 2017-09-15T16:48:05.000+05:30
Ref: https://github.com/coveralls-clients/coveralls-python/blob/master/setup.py#L29
diff --git a/.travis.yml b/.travis.yml
@@ -9,7 +9,6 @@ before_install:
   - pip install coveralls
 install:
   - pip install -e .
-  - pip install coverage
 
 script: nosetests -w tests/unit --with-coverage --cover-package=quickbooks
 after_success:
