Mostly style changes to chapter 2 examples

These are mostly style changes, such as:
- Space between parameters in function calls/argument lists
- Semi-colons after function-as-variable statements but not after function blocks
- Removal of trailing whitespace

Note that the last two were caught by my JSHint plugin in SublimeText, which I recommend setting up in your IDE of choice and configuring per agreed upon project conventions.

There were several things I didn't change, despite incompatibility with Khan style:
- I kept function draw(), etc, as blocks instead of statements, per your expressed preference.
- I kept indenting at 2 spaces (we use 4, but 2 spaces appears to be more common nowadays).
- We don't support the 2-argument fill() commands currently, we pop up a message about wrong number of arguments. I could fix that, but I worry some people accidentally use 2 without realizing its an alternate syntax.

I'll make comments inline if there were other things I changed.