Remove Package.swift, SnapKit is not SwiftPM compatible anyways

Package.swift

@@ -1,37 +0,0 @@
-// swift-tools-version:4.0
-//
-//  SnapKit
-//
-//  Copyright (c) 2011-Present SnapKit Team - https://github.com/SnapKit
-//
-//  Permission is hereby granted, free of charge, to any person obtaining a copy
-//  of this software and associated documentation files (the "Software"), to deal
-//  in the Software without restriction, including without limitation the rights
-//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-//  copies of the Software, and to permit persons to whom the Software is
-//  furnished to do so, subject to the following conditions:
-//
-//  The above copyright notice and this permission notice shall be included in
-//  all copies or substantial portions of the Software.
-//
-//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-//  THE SOFTWARE.
-
-
-import PackageDescription
-
-let package = Package(
-    name: "SnapKit",
-    products: [
-        .library(name: "SnapKit", targets: ["SnapKit"]),
-    ],
-    targets: [
-        .target(name: "SnapKit", path: "Source"),
-        .testTarget(name: "SnapKitTests", dependencies: ["SnapKit"]),
-    ]
-)