Adding requirements.txt and dependencies in .travis.yml

Author: execat

.travis.yml

@@ -8,6 +8,7 @@ python:
 # command to install dependencies
 install:
   - pip install .
+  - pip install python-dateutil
   - pip install -r requirements.txt
 # command to run tests
-script: nosetests 
+script: nosetests

requirements.txt

@@ -0,0 +1,2 @@
+pycontracts
+requests