Remove nil return value of #overwrites.

The method documentation explains the void return value, no need to explicitly provide a nil value.
Correct old stylistic choices.
Condense heavily-nested methods.
Reformat script documentation.
Fix minor YARD formatting errors.
Add newline to end of file.
Merge branch 'unstable'
Update error testing for overwrites.
Remove Class#new alias, condense MethodData methods.