fix typo in travis config

Author: dcrosta

.travis.yml

@@ -11,4 +11,4 @@ services: mongodb
 install: pip install -r test-requirements.txt -e .
 script: py.test --tb=native tests
 before_script:
-  - mongo test_db --eval 'db.createUser({user:"flask", pwd:"pymongo", roles:["readWrite"]})
+  - mongo test_db --eval 'db.createUser({user:"flask", pwd:"pymongo", roles:["readWrite"]})'