update readthedocs (#342)

* update readthedocs

docs/conf.py

@@ -13,7 +13,6 @@
 from recommonmark.transform import AutoStructify
 from recommonmark.parser import CommonMarkParser
 import os
-import paddlehub as hub
 import sys
 sys.path.insert(0, os.path.abspath('../paddlehub'))
 

docs/requirements.txt

@@ -3,4 +3,3 @@ sphinx-argparse==0.2.5
 sphinx-markdown-tables==0.0.12
 sphinx-rtd-theme==0.4.3
 recommonmark==0.6.0
-paddlehub