Upgraded test dependencies.

Author: yellowcap

.travis.yml

@@ -23,10 +23,10 @@ before_script:
 
 install:
   - pip install -e .
-  - pip install psycopg2-binary==2.7.7
-  - pip install flake8==3.7.7
-  - pip install isort==4.3.15
-  - pip install coverage==4.5.3
+  - pip install psycopg2-binary==2.8.4
+  - pip install flake8==3.7.9
+  - pip install isort==4.3.21
+  - pip install coverage==4.5.4
   - pip install coveralls
   - pip install mock