Merge pull request #4 from vapor-community/swift4

Add Swift 4 support

.gitignore

@@ -4,3 +4,4 @@
 /*.xcodeproj
 Package.pins
 DerivedData/
+Package.resolved

.travis.yml

@@ -5,7 +5,7 @@ language: generic
 sudo: required
 dist: trusty
 
-osx_image: xcode8.3
+osx_image: xcode9
 before_install:
     - if [ $TRAVIS_OS_NAME == "osx" ]; then
             brew tap vapor/tap;

Package@swift-4.swift

@@ -0,0 +1,17 @@
+// swift-tools-version:4.0
+
+import PackageDescription
+
+let package = Package(
+    name: "SwiftMarkdown",
+    products: [
+        .library(name: "SwiftMarkdown", targets: ["SwiftMarkdown"]),
+    ],
+    dependencies: [
+    	.package(url: "https://github.com/brokenhandsio/cmark-gfm.git", .upToNextMajor(from: "1.0.0")),
+    ],
+    targets: [
+        .target(name: "SwiftMarkdown", dependencies: ["cmark"]),
+        .testTarget(name: "SwiftMarkdownTests", dependencies: ["SwiftMarkdown"]),
+    ]
+)

README.md

@@ -1,6 +1,6 @@
 # Markdown
 
-[![Language](https://img.shields.io/badge/Swift-3-brightgreen.svg)](http://swift.org)
+[![Language](https://img.shields.io/badge/Swift-4-brightgreen.svg)](http://swift.org)
 [![Build Status](https://travis-ci.org/vapor-community/markdown.svg?branch=master)](https://travis-ci.org/vapor-community/markdown)
 [![GitHub license](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/vapor-community/markdown/master/LICENSE)
 
@@ -41,5 +41,5 @@ For more information on the available options, see [`cmark`](https://github.com/
 ## Swift Package Manager
 
 ```swift
-.Package(url: "https://github.com/vapor-community/markdown.git", majorVersion: 0, minor: 3)
+.package(url: "https://github.com/vapor-community/markdown.git", .upToNextMajor(from: "0.4.0"))
 ```