Updated Install Documentation to Have Better Specifics

Hey guys,

I think this is different than what the other open PR is addressing, but I apologize if there's overlap. I added some specifics (including Arduino versions) and where you put the the RFduino libraries, as it's slightly different for ```1.5.8``` (seems like the docs are for ```1.5.6```). Also added some code ticks for readability.

Thanks for all your work guys! Love the project :+1: