[iOS8] fix device family string in order to select device
[iOS8] add "device_name" parameter

Usage:
	$ rake device_name="iPad Air"

We can use the following device name for iOS 8 simulator.
	"iPhone 4s"
	"iPhone 5"
	"iPhone 5s"
	"iPad 2"
	"iPad Retina"
	"iPad Air"
	"Resizable iPhone"
	"Resizable iPad"
[spec] Add spec helpers subdirs to #spec_files.

Signed-off-by: Eloy Durán <eloy.de.enige@gmail.com>
[OSX] fix a wrong default deployment_target on OS X 10.8

http://hipbyte.myjetbrains.com/youtrack/issue/RM-524

'10.8' should be used as default deployment target on OS X 10.8.
However, '10.9' was used.
[OSX] add CoreServices to detect OS X version to convert NSKnownKeysDictionary into NSDictionary
[OSX] fix a 'not precompiled' error if specify old version as deployment_target on Yosemite

http://hipbyte.myjetbrains.com/youtrack/issue/RM-525
2.30