Swift4 KeyPath Support

[kenji21]

Tailor Version: v0.12.0

Swift Version: 4.0

Platform (Mac/Linux/Windows/CI): Mac

Installation Method: Homebrew

Steps to Reproduce Issue

1. Have a swift file containing \SomeClass.someProperty, like this:

@objc class SomeClass: NSObject {
    var someProperty: Int
    init(someProperty: Int) {
        self.someProperty = someProperty
    }
    func keyPathTest() -> String {
        return #keyPath(someProperty)
    }
    func keyPathTestForSwift4() -> KeyPath<SomeClass, Int> {
        return \SomeClass.someProperty
    }
}

Expected Behavior

Macros.swift should be parsed successfully

Actual Behavior

./Macros.swift could not be parsed successfully, skipping...

[kenji21]

PR #493 just pushed