Bump Buildbot extension to version 0.9.0 from 0.8.4 to include the changes made

in r286141.

TBR=miket@chromium.org

Review URL: https://codereview.chromium.org/465273003

Cr-Commit-Position: refs/heads/master@{#289351}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289351 0039d316-1c4b-4281-b951-d872f2087c98

chrome/common/extensions/docs/examples/extensions/buildbot/manifest.json

 {
   "name": "Chromium Buildbot Monitor",
-  "version": "0.8.4",
+  "version": "0.9.0",
   "description": "Displays the status of the Chromium buildbot in the toolbar.  Click to see more detailed status in a popup.",
   "icons": { "128": "icon.png" },
   "background": {