hopefully added cbc and glpk tests

.travis.yml

@@ -8,10 +8,11 @@ python:
   # does not have headers provided, please ask https://launchpad.net/~pypy/+archive/ppa
   # maintainers to fix their pypy-dev package.
   - "pypy"
-before_install: sudo apt-get install tree
+before_install: 
+  - sudo apt-get install glpk
+  - sudo apt-get install coinor-cbc
 # command to install dependencies
 install:
   - pip install .
-before_script: tree
 # command to run tests
 script: pulptest