Completed issue 48: Adds bobbing to thangs with 'bobs' property.
Thangs with 'bobs' must also set 'bobSpeed' and 'bobHeight'
Refactored ticker, fixed from all instances were using same ticker.
Merge pull request #73 from TomSteinbrecher/master

Completed #48: Adds bobbing to thangs with 'bobs' property.
Fixed a GitHub link.