[BLD] Run 'full' test suite on Travis, including 'slow' tests

There's no reason *not* to run the full test suite on Travis, so long
as we fit in under the time limit. And no way to find out if we fit
under the time limit except to try ;-).

.travis.yml

@@ -45,7 +45,7 @@ script:
   - cd empty
   - INSTALLDIR=$(python -c "import os; import numpy; print(os.path.dirname(numpy.__file__))")
   - export PYTHONWARNINGS=default
-  - python ../tools/test-installed-numpy.py
+  - python ../tools/test-installed-numpy.py --mode=full
   # - coverage run --source=$INSTALLDIR --rcfile=../.coveragerc $(which python) ../tools/test-installed-numpy.py
   # - coverage report --rcfile=../.coveragerc --show-missing
 notifications: