All components use range 0.0-1.0

Fixes issue #5
Update components using message lock

Must be done or else Juce will assert and risk of thread naughtiness will
ensue.
Free resource cache from MainComponent in dtor

Also add documentation stating that this must be done or else memory will be
leaked. Fixes issue #1.
Indenting, minor cleanups
Cache images, calculations in fields

Fixes issue #10