MAINT calculate coverage only for python3.5

Author: mfeurer

.travis.yml

@@ -16,7 +16,7 @@ env:
   - MODULE=openml
   matrix:
   - DISTRIB="conda" PYTHON_VERSION="2.7" NUMPY_VERSION="1.10.4" SCIPY_VERSION="0.17.0" CYTHON_VERSION="0.21"
-  - DISTRIB="conda" PYTHON_VERSION="3.4" COVERAGE="true" NUMPY_VERSION="1.10.4" SCIPY_VERSION="0.17.0" CYTHON_VERSION="0.23.4"
+  - DISTRIB="conda" PYTHON_VERSION="3.4" NUMPY_VERSION="1.10.4" SCIPY_VERSION="0.17.0" CYTHON_VERSION="0.23.4"
   - DISTRIB="conda" PYTHON_VERSION="3.5" COVERAGE="true" NUMPY_VERSION="1.10.4" SCIPY_VERSION="0.17.0" CYTHON_VERSION="0.23.4"
 install: source ci_scripts/install.sh
 script: bash ci_scripts/test.sh