Remove unnecessary coverage directive

.travis.yml

@@ -34,7 +34,7 @@ script:
     - "echo 'backend.qt4 : PyQt4' >> $HOME/.matplotlib/matplotlibrc"
     - mkdir for_test
     - cd for_test
-    - nosetests-$PYVER --exe -v --cover-package=skimage --with-doctest skimage
+    - nosetests-$PYVER --exe -v --with-doctest skimage
     # Change back to repository root directory and run all doc examples
     - cd ..
     - for f in doc/examples/*.py; do $PYTHON "$f"; if [ $? -ne 0 ]; then exit 1; fi done