Build - move to node-sass

Removing ruby requirement for build system greatly simplifies setup
Meta - Remove worlds from git
Meta - Lock node-server to commit SHA
Build - Add example_world to repo, instruction to copy it over as a starting point

contains snapshot of kumavis server

At this point the server reads from the db at start, and writes to it on block change. This makes a mess of git so we ignore it. But then we need to provide a starting point.