Select archive extension based on `version` and `install_method`

I hate myself for this, and I'm pretty sure some kittens died in the
making of this code.
Prefer `%()` over double quotation marks (`""`)
Remove `build` as root

Because reasons. Fuck.
Extract `kafka_src` to helper method
Add hackyish support for building Kafka v0.8.1 from source

Maaaan, this fucking mess I tell you. v0.8.1 switched from 'sbt' to 
'gradle', and it was just a cluster fuck to actually construct a
'release' tar.gz archive. Google is my best friend, always and forever.

I'm not happy about this current solution, and I'm not done with it yet.
There's plenty of room for improvement and making things pretty.
Just you wait.
Extract `kafka_target_path` to helper method
Update service related integration tests to be less picky

v0.8.1 doesn't log the same messages as v0.8.0 (for some reason), there's
been changes to capitalisation and whatnot.
Update default kafka and scala versions

* kafka, v0.8.0 -> v0.8.1
* scala, v2.8.0 -> v2.9.2

The future is now, deal with it.
Bump ZK connection timeout in .kitchen.yml
Update default kafka version to v0.8.1.1

Really need to fix the tests to be less annoying when updating versions.
Add new `log` related attributes for kafka > v0.8.0
Add new `advertised` attributes for kafka > v0.8.0
Change default port to 9092
Update README w/ new attributes and updated defaults

[ci skip]
Set `scala_version` in attributes file instead of recipes
Merge branch 'v0.8.1-support'