Run unit tests on Travis

Closes #2

.travis.yml

@@ -0,0 +1,13 @@
+---
+
+language: python
+python:
+  - "2.7"
+  - "3.4"
+  - "3.5"
+  - "3.6"
+install:
+  - pip install -r requirements.txt
+  - pip install .
+script:
+  - pytest

requirements.in

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+cffi
+redis
+pytest

requirements.txt

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+#
+# This file is autogenerated by pip-compile
+# To update, run:
+#
+#    pip-compile --output-file requirements.txt requirements.in
+#
+atomicwrites==1.2.1       # via pytest
+attrs==18.2.0             # via pytest
+cffi==1.11.5
+more-itertools==4.3.0     # via pytest
+pluggy==0.7.1             # via pytest
+py==1.6.0                 # via pytest
+pycparser==2.19           # via cffi
+pytest==3.8.1
+redis==2.10.6
+six==1.11.0               # via more-itertools, pytest