[#7] Add command to change back to working directory

Author: meatballs

.travis.yml

@@ -10,6 +10,7 @@ before_install:
   - git clone https://github.com/Axelrod-Python/TourExec.git /tmp/TourExec
   - cd /tmp/TourExec
   - sudo make install
+  - cd $TRAVIS_BUILD_DIR
 install:
   - pip install -r requirements.txt
   - pip install pytest