Update releasing guide to use pulp publish

Previously this was done in Travis CI but there's really no good reason to
manually push branches and let CI publish instead of just using the publish
command directly.

Releasing.md

@@ -15,7 +15,9 @@
    notes for v<new version number>`.
 4. Run `pulp version` in the project root. This will check the project for any
    issues and create a new version tag and empty checkpoint commit.
-5. Push the release notes and version commit and version tag.
+5. Run `pulp publish` in the project root.  This will publish the commits & tag
+   to github, will publish the package to bower, and will push documentation to
+   pursuit.
 6. If you are pushing a non-patch release, create and push a branch named with
    the version series, i.e. `v0.1.x`.
 7. [Create the release on