Add placeholder mechanism to store and trigger events.

- Rename Events to EventRepository.
Fix #execute to accept any number of arguments.
Fix tests for EventRepository.
Remove guard.
Remove unnecessary lines.
Use defined entity.
Simplify Geometry class.
Remove toggle event, add coverage for EventRepository.
Composition tests leak, add result which sometimes comes out.
Make life difficult, make tests parallel.
Add 'colour_reset' style to reset colours to terminal defaults.
Capture any uncaught exception to the log file.
Add simple example app.
Return meaningful type form #by_input.

Rather than return NilClass, this has been changed to return FalseClass.
Move #by_layer to private.
Not sure why this key was a string.
Require 'ruby-prof' in method.
Fix test description.
Single quote for non-interpolated strings.
Remove extra brackets.