Fix for IE7 compatibility

IE7 doesn't support Array.isArray(). Use object.prototype instead.
Merge pull request #2 from mattwelch/master

Fix for IE7 Array.isArray() problem.

Per discussion with MattWelch, this may look and feel hacky, but it's legit code that uses an older convention for ducktyping an array since ie 7 (or rather ie 10 forced into ie7 mode) doesn't support isArray. Matt tested in ff, chrome, safari, and stock ie10.