Fixed Crash on 32bits Architecture

[RuiAAPeres]

This fixes issue #13

[kean]

Thanks, I'll take a look a little bit later. I guess that NSProcessInfo.processInfo().physicalMemory returns invalid value like UInt64.max starting with iOS 9 (can't test atm). If it does then we should either find an alternative API or just always return some default value as a recommendedCacheTotalLimit. Returning Int.max is unreasonable, 32-bits devices can't even address more memory.

[RuiAAPeres]

I tested that on the simulator (my carthage file is currently pointing to that commit) and it's working. But we can look for another alternative.

[kean]

Oh, actually physicalMemory works fine. It's just that you have more than 8 Gb of RAM :)

(1024 * 1024 * 1024 * 16) * 0.2 = 3 435 973 836
3 435 973 836 > 2 147 483 647 (Int.max on 32 bit)