Do not allow fields outside of classes.
Allow 16 arguments, and handle going over that correctly.
Clean up constructor tests.
Move debug code into separate module.
Fix compiling constructors.
Get binary_trees benchmark working.

Wren is actually doing well in it:

wren      mean: 1.9441 median: 1.9428 std_dev: 0.0260
lua       mean: 3.5992 median: 3.6033 std_dev: 0.0156
python    mean: 3.6667 median: 3.7097 std_dev: 0.1340
ruby      mean: 1.3941 median: 1.3914 std_dev: 0.0091
Ignore scratch script.