Fix requirements for travis

base_requirements.txt

+lxml==3.0.1
+mock==0.8.0
+nltk==2.0.3
+nose==1.2.1
+path.py==3.0
+pip
+pylint==0.26.0
+pytz==2012h
+scikit-learn==0.12.1

requirements.txt

+-r base_requirements.txt
 boto==2.6.0
 coverage==3.5.3
-lxml==3.0.1
-mock==0.8.0
-nltk==2.0.3
-nose==1.2.1
 scipy==0.11.0
-path.py==3.0
-pip
-pylint==0.26.0
-pytz==2012h
-scikit-learn==0.12.1
-sphinx
-django-sphinx-autodoc