Update documentation to reflect (anticipated) v0.5.0
Add page about usage of SBT plugin

Also fixes #37: Document how to cross build
Improve documentation structure
Add links to CLI distribution
Add links to API docs
wip tutorial step 1
wip tutorial step 0
wip tutorial step 2
wip tutorial drop references to standalone distro
wip tutorial step 3
wip tutorial step 4
wip tutorial step 5 partial
wip tutorial use scala 2.11.1
wip tutorial add section headers
wip tutorial step 5
wip tutorial step 8