Make README more descriptive and make use of Markdown

I have allowed myself to restructure your README file, because I think it was looking pretty pathetic for such a great project. I've made use of Markdown as all of the major hosting platforms (github.com, gitorious.org, etc.) have support for it included while the source is still quite readable for humans.

I've added a couple of sections to better describe the project. Most of it is copied off from somewhere else (e.g. your project page). I've also added sections for donations and added logos for all kinds of things. **Please** make sure to check the links and/or add things you might consider useful. You can take a look at [this](https://github.com/johnpatcher/ols/blob/feat/README/README.md) to get a preview of the new version. Hopefully you like it ;).