adding mac support!

umm...this is my first pull request on github, hopefully i didn't screw anything up.

the first commit is pretty big looking, but a lot of it is additions - i duped the c_source folder and made it a c_source_mac folder. I also did a 'lime test mac' which generated all the mac files.  

The biggest changes I actually made was commenting some stuff out in main.cpp to get it mac-friendly, and also changing MenuState.hx so that the server and client pointed to 'localhost'.  

I'm probably going to figure out iOS support for this next if I am able, so it's likely that my 'localhost' change in MenuState is temporary.

I also updated the README file to include information about the mac build, because it currently requires an attention to detail in order for it to work :)

Thanks for you help with this! hopefully I didn't screw up the fork/pull business!