Update Travis, Remove requirements.txt

Since setup.py is handling requirements now, I think I can remove
requirements.txt.  Also, travis needs to be updated to use py.test

.travis.yml

@@ -8,6 +8,6 @@ python:
   - 2.7
   - pypy
 install: 
-  - pip install -r requirements.txt --use-mirrors
+  - pip install PyYAML pytest --use-mirrors
   - if [ $WITH_REQUESTS = "True" ] ; then pip install requests; fi
-script:  python test.py
+script:  py.test

requirements.txt

@@ -1 +0,0 @@
-PyYAML