JS Style Guide: Add rules for constructor invocation

Ref https://github.com/jquery/jquery/pull/1856#issuecomment-65346516

These reflect my personal preference for explicit clarity (especially around whitespace-preceding keyword operators) and could easily be changed; I just want to get some clear guidelines published.
My understanding was that _grouping_ parenthesis don't need inside spaces, but on closer inspection it appears that we only relax them for wrapping assignments. Must be spending too much time in old code.