Remove some demos which have been broken for a long time

We have no immediate plans to fix these
Fix use of backgroundColor in demo animations

This was broken by 1b757b12664f87e535e222fb9d682c0dc27b7865
Update demos and README.md after renaming Timing.duration to Timing.iterationDuration

This was renamed in 5ee65b94527a1c0808d89f2ba229d88303310332
Merge pull request #395 from steveblock/demoFixes

Demo fixes