Pin Sphinx to <1.2

1.2 was just released and has a bug that causes builds to fail with
the error:

  error: 'source_dir' must be a directory name (got `...doc/source`)

See: http://bugs.python.org/issue19570
and: https://bitbucket.org/birkenfeld/sphinx/pull-request/193/builddoc-shouldnt-fail-on-unicode-paths/diff

Change-Id: I8a27127dd298f0c8a905c4ab17b3112e010059fd

test-requirements.txt

@@ -1,6 +1,6 @@
 flake8==2.0
 coverage
-sphinx
+sphinx>=1.1.2,<1.2
 docutils==0.9.1
 discover
 fixtures>=0.3.12