Adds basic support for the Swift programming language

Text only lexer for now until Pygments catches up

samples/Swift/section-55.swift

@@ -0,0 +1,20 @@
+class Square: NamedShape {
+    var sideLength: Double
+
+    init(sideLength: Double, name: String) {
+        self.sideLength = sideLength
+        super.init(name: name)
+        numberOfSides = 4
+    }
+
+    func area() ->  Double {
+        return sideLength * sideLength
+    }
+
+    override func simpleDescription() -> String {
+        return "A square with sides of length \(sideLength)."
+    }
+}
+let test = Square(sideLength: 5.2, name: "my test square")
+test.area()
+test.simpleDescription()