* increased xcode requirement to xcode 6.2+ as the clang version shipping with xcode 6.1 is still the outdated one from 6.0 (note: using a custom built clang 3.5 does of course work with any xcode version)
 * updated/fixed the xcode project (header search should now be ../ instead of ./ so that floor header files are found when it isn't "installed" to a /usr include path yet)