MAINT: Upgrade requests 2.7.0 -> 2.9.1

docs/source/whatsnew/0.8.4.txt

@@ -122,6 +122,8 @@ Maintenance and Refactorings
 * Asset databases now contain version information to ensure compatibility
   with current Zipline version (:issue:`815`).
 
+* Upgrade requests version to 2.9.1.
+
 Build
 ~~~~~
 

etc/requirements.txt

@@ -22,7 +22,7 @@ python-dateutil==2.4.2
 six==1.9.0
 
 # For fetching remote data
-requests==2.7.0
+requests==2.9.1
 
 Cython==0.22.1