Number.prototype.toInteger was removed from ES6

https://github.com/rwaldron/tc39-notes/blob/master/es6/2013-07/july-25.md#consensusresolution-2
Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
Merge pull request #130 from rwaldron/remove-number-tointeger

Number.prototype.toInteger was removed from ES6