Keyboard.js does not reflect Phaser.Key changes

Calling justPressed or justReleased on Phaser.Keyboard throws an exception. Changed to reflect new method names in Phaser.Key

I imagine you'd want these methods renamed as well, but it appears to be called by a few other classes and I didn't want a huge pull-request.
Merge pull request #1349 from neurofuzzy/patch-1

Keyboard.js does not reflect Phaser.Key changes