Added coloring for dashed-names and #{string interpolations}

I recently started hacking in LiveScript - after a year or so of writing CoffeeScript - and I fell in love with it. I looked for LS support for Emacs. I found at least 4 modes, but they were rather primitive. This one is the most feature complete and so I'm using it now. I already wrote a few lines of code for it and I thought that maybe someone else than me would like to have them. So here is pull request. Besides what I wrote in the commit message, `livescript-mode.el` now compiles without warnings.

I'm somewhat disappointed that this mode is not maintained anymore (I read this on the Issues page). I'm not immediately interested in taking it over, but I probably will hack on it some more, so it would be great if you could find some time to review my pull requests and merge them if they're ok.