Removed line to install sagemath (should be done by dependency)

Author: mmasdeu

.travis-test.sh

@@ -4,7 +4,6 @@
 # notice and this notice are preserved.  This file is offered as-is,
 # without any warranty.
 set -e
-$HOME/SageMath/sage -pip install --user --upgrade -v -i https://pypi.python.org/pypi sagemath # Check that Sage is installed
 $HOME/SageMath/sage -pip install --upgrade --no-index -v .
 $HOME/SageMath/sage setup.py test
 (cd docs && $HOME/SageMath/sage -sh -c "make html")