Enable Travis

This commit enables running the unit tests on Travis for Python 2.6,
2.7, 3.3, and 3.4.  Note that Travis does not support Python 2.4, so
we cannot test there.

.travis.yml

@@ -0,0 +1,10 @@
+language: python
+python:
+    - 2.6
+    - 2.7
+    - 3.3
+    - 3.4
+
+install: pip install -r test-requirements.txt
+
+script: python setup.py nosetests --verbosity=3

test-requirements.txt

@@ -0,0 +1,2 @@
+mox
+nose

tox.ini

@@ -8,9 +8,7 @@ envlist = py24,py26,py27,py33,py34
 
 [testenv]
 commands = nosetests {posargs}
-deps =
-    mox
-    nose
+deps = -r{toxinidir}/test-requirements.txt
 
 # At some point we should enable this since tox expects it to exist but
 # the code will need pep8ising first.