pep8 check in travis

Author: longbai

.travis.yml

@@ -4,7 +4,9 @@ python:
   - "2.7"
 install:
   - "pip install coverage --use-mirrors"
+  - "pip install pep8 --use-mirrors"
 before_script:
+  - "pep8 --max-line-length=160 ."
   - export QINIU_ACCESS_KEY="X0XpjFmLMTJpHB_ESHjeolCtipk-1U3Ok7LVTdoN"
   - export QINIU_SECRET_KEY="wenlwkU1AYwNBf7Q9cCoG4VT_GYyrHE9AS_R2u81"
   - export QINIU_TEST_BUCKET="pysdk"