Add HOWTO

[JoeyAcc]

To be honest I have no clue how to use this crate.
And that is after both glancing at the code as well as trying an API model similar to the one offered by serde_json. And none of it even compiles.

Therefore I think it would be very useful to add a section in the README.md detailing how to actually use the code in this crate. Could that be added?

[oli-obk]

Yea... I never got around to doing that. I'll include it in the 0.9 update (I need to grok the API again myself first ;) )