add PEP8 check in travis CI

.travis.yml

@@ -9,9 +9,10 @@ cache:
 before_install:
   - sudo apt-get update -qq
   - sudo apt-get install -qq build-essential libssl-dev swig python-m2crypto python-numpy dnsutils
-  - pip install m2crypto salsa20
+  - pip install m2crypto salsa20 pep8
   - sudo tests/socksify/install.sh
 script:
+  - pep8 .
   - python tests/test.py -c tests/table.json
   - python tests/test.py -c tests/aes.json
   - python tests/test.py -c tests/salsa20.json