Added composable versions of base and ruby-rvm playbooks. Need to update other playbooks then delete old versions
Added back warning message in Ruby playbook as still a need to exit and then re-log in to terminal
Added roles for:
1. Oracle Java (6 and 7, settable by a variable)
2. sbt
3. Scala
4. Thrift

Still need to port over some old playbooks to composable roles (e.g. postgres-8.4, play-framework) and add oh-my-zsh
Refactored old playbook into a number of new roles (grunt / jekyll / yui-compressor) for Snowplow-specific development environments (Javascript and website)
Explained problem associated with composing playbooks with gem installations directly following RVM installation in ruby-rvm/tasks/main.yml file
Removed legacy playbooks (i.e. those that have now been refactored)