Adds basic support for the Swift programming language

Text only lexer for now until Pygments catches up

samples/Swift/section-39.swift

@@ -0,0 +1,8 @@
+func makeIncrementer() -> (Int -> Int) {
+    func addOne(number: Int) -> Int {
+        return 1 + number
+    }
+    return addOne
+}
+var increment = makeIncrementer()
+increment(7)