Add boolean diff mode that aborts as soon as a difference is found

[nhooey]

Sometimes you just want to know if two things differ deeply, but aren't interested in the details. A diff mode that returns a boolean and aborts early would perform much better than the default implementation.

[sebn]

Woudn't lodash's _.isEqual (or something equivalent) do the trick, since we can install it on its own and it doesn't have any dependency? So it doesn't really have to be part of deep-diff... or did I miss anything?