Improve Kontrol docs

[Nickstr]

Right now the docs don't mention how to actually install and run Kontrol.

[fatih]

Hi @Nickstr. Thanks for it. I'll add some docs asap this week :+1: For now please have a look at kontrol tests:

https://github.com/koding/kite/blob/master/kontrol/kontrol_test.go

In the init() function you can see how to run a simple Kontrol and the TestMultiple shows an example of multiple clients registering to Kontrol and being fetched again from Kontrol.

[cenkalti]

@fatih please don't forget to add how to create inital keys for kontrol. I forgot how to do it and kontrol's flags are not intuitive.

[techjanitor]

I added some instructions in #94

[schorsch]

+1 after reading the code for an hour and trying to puzzle things together. Btw any progress on https://github.com/koding/kite/issues/39 ?