Updated build instructions about ant

+ Added instructions for using ant to generate sources
+ Split up build instructions from run instructions
IntelliJ should ship with ant.  If for some reason they don't have the command line tool (or can't find it) they can use **Build > haskforce > generate.sources**.  Also, there are a lot of folks using Windows, Linux, etc.  Might not want to give off the impression that this is only for Mac.

I'll go ahead and merge these in though and make my nit-picky edits :)