added travis

.travis.yml

+language: python
+python:
+  - "2.6"
+  - "2.7"
+  - "3.2"
+  - "3.3"
+  - "3.4"
+  - "3.5"
+  - "3.5-dev" # 3.5 development branch
+  - "3.6"
+  - "3.6-dev" # 3.6 development branch
+  - "3.7-dev" # 3.7 development branch
+  - "nightly" # currently points to 3.7-dev
+# command to install dependencies
+install: "pip install -r requirements.txt"
+# command to run tests
+script: pytest
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