Remove docutils pin

This was added to work around bug 1091333.  A new sphinx has been
released and so this is no longer necessary.

Also update sphinx requirement with global requirements.

Change-Id: I9107884d964757a9154bdd1feb4ea6df4e9df43e

test-requirements.txt

@@ -1,9 +1,8 @@
 # Nodepool uses hacking for its dependencies
 hacking>=0.8,<0.9
 coverage
-sphinx>=1.1.2,<1.2
+sphinx>=1.1.2,!=1.2.0,!=1.3b1,<1.3
 sphinxcontrib-programoutput
-docutils==0.9.1
 discover
 fixtures>=0.3.12
 python-subunit