Update UIViewController+PromiseKit.m
Update UIViewController+PromiseKit.m

<objc/objc-runtime.h> does not seem to be available when compiling to an iOS device.
pgherveou/PromiseKit,mxcl/PromiseKit,allen-zeng/PromiseKit,pgherveou/PromiseKit,allen-zeng/PromiseKit,pgherveou/PromiseKit,mxcl/PromiseKit,mxcl/PromiseKit