Better doc building on travis.

This makes two changes:

* Force `tox` to use a new version of `sphinx`, since we depend on features
  from the `1.3` branch.

* Tweak the `build-docs` script to build on any push. The logic for skipping
  the build in the case of a non-master push was originally in place to
  prevent new docs from being pushed live, but we opted to make that manual
  instead. As a result, this just masks docs errors in pull requests.

1 files changed, 1 insertions, 1 deletions

diff --git a/tox.ini b/tox.ini
index 46724cd..639b56b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -42,7 +42,7 @@ deps =
     {[testenv:cover]deps}
     python-gflags
     pyyaml
-    sphinx
+    sphinx>=1.3b2
     sphinx-rtd-theme
 commands = {toxinidir}/scripts/build-docs