CLI: Support a maxErrors option to limit the number of reported errors (fixes #664, fixes #238)

I started on #664 and remade this to be simpler and non-static.
I still think the max errors exceeded itself should be an error, like in JSHint.

In fact, I still contend that all info from JSCS should be reported as style violations, like we did when deprecated rules or converted the errors from esprima.