upgrade boto to match platform

requirements.txt

 -r base_requirements.txt
-boto==2.6.0
+boto==2.13.3
 coverage==3.5.3
 scipy==0.11.0
 scikit-learn==0.12.1
 sphinx
 django-sphinx-autodoc
-nltk==2.0.3
\ No newline at end of file
+nltk==2.0.3