Love 0.8.0 compatibility changes for submission to Vapor

Hi,

First of all, I would like to say congrats to you all for this game, which is fantastic.
I had the pleasure to play it a while ago, and I löved it.
Well, [Vapor](https://github.com/josefnpat/vapor) is a distribution client for Löve games (maintained by @josefnpat), and it is quite nice. In a nutshell, a [Steam](http://steamcommunity.com) for Löve games.
I wanted to submit this game, but it had to be compatible with [Löve 0.8.0](http://love2d.org/wiki/0.8.0).
Hence the actual pull request.
I made a couple of slight changes to the code to so that the game would be fully playable with the latest 0.8.0...I also made a quick (and dirty ?) fix along for joystick handling, which [were causing the game to crash][https://github.com/josefnpat/vapor/issues/88#issuecomment-23962443).
In case you are okay with these changes, you can build a new .love file, host it wherever you want, we'll add it to Vapor. This is such a solid prototype, so let the whole world give it a try.
Thanks reading,

Best regards,
Roland.