Add "get started" page

[FroMage]

Tomaz Cerar suggested we add something like Java's http://docs.oracle.com/javase/tutorial/getStarted/

what do I download/build/compile to start working with? how do I work with? How tooling works? how do I run compiler? and many more questions like this.

I figure this is a good idea and we could even link to it from the dowload page as: "what's the next step now?"

[rdruss]

Related to the getting started experience, once there is Maven support in Ceylon, perhaps a JBoss Forge plugin would be useful.