Use CSS class constant in zoomslider.
Add fallback when examples are opened w/ file://.

When opening an example through the `file:`-protocol, e.g.
`file:///ol3/examples/full-screen.html` our `loader.js` would inject
a `<script>` tag with a `src` pointing to an illegal URL
`http://:9810/compile?mode=ADVANCED&id=full-screen`.

This changes the respective logic, so that in the case that we are accessed
through the `file:`-protocol, we fallback to using `localhost` as hostname
for the plovr-compiler.

The examples that do not use XHR (like e.g. `wms-capabilities.html`) now
work as expected when accessed through `file:`-protocol.
Merge pull request #377 from marcjansen/use-css-constant

Use CSS class constant in zoomslider.
Reformatted and gjslinted example-screenshot.js.
Restrict progressbar to fixed width.

As more and more examples will be processed with this script, the
progresbar would grow way too long. This commit makes the width of
the bar fixed. Every character in the bar now equals 5% progress,
regardless of the number of examples.
Merge pull request #378 from marcjansen/examples-file-protocol

Add fallback host when examples are accessed through file:-protocol.
Merge pull request #379 from marcjansen/progressbar

Restrict width of progressbar in example-screenshot.js