This reverts 4d619d71b1 (see #1527), going back to what we had after e13075f6ff (see #881).
To avoid the 404 in the hosted examples, the css is copied to the same relative path when hosted as during development.
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.
