Linted jquery.pailer.js, added missing semicolons.

There are not functional changes here, only cosmetic. Added missing
semicolons, used triple equals to test equality, and preferred
unquoted hash keys where appropriate.

Review: http://reviews.apache.org/r/16028
Made pailer scrollable in Chrome and Safari.

After a change to fix the pailer in Firefox, Chrome and Safari broke.
By removing the inner <code> block and using just a <pre> element, the
calculations done by the pailer work again and in all 3 browsers.

The style changes simplified the CSS.

In JS, references to the DOM are kept in variables to prevent unneeded
trips to the DOM on window resizing.

Review: http://reviews.apache.org/r/16029
Removed unused 'slaves' table from home page.

The slaves table was removed from the home page a while ago, and so
the table was not ever being referenced.

Review: http://reviews.apache.org/r/16030
Added git sha, tag and branch in state.json.

Exposing build revisions and branch names can help diagnosing problems
with slaves and masters in development settings.

This patch fetches git sha, tag and branch of repo (if available) and
fills option variables BUILD_GIT_SHA, BUILD_GIT_TAG and BUILD_GIT_BRANCH
accordingly. If variables are set, master and slave state.json expose
and sets fields "git_sha", "git_tag" and "git_branch".

Review: https://reviews.apache.org/r/15169