Remove kittens stuff left over from the tutorial
Stop treating highlight as button

Highlight is a checkbox, so don't treat it as a button and send its
checked state as a parameter to converter instead.
Improve test diagnostics and wrap long lines
Deal with decimal points

Improve regexp to match a number with decimal points, parse it
accordingly and add a couple of tests for it.
Fix overly greedy number matching
Use highlight parameter in matching code