Adds basic support for the Swift programming language

Text only lexer for now until Pygments catches up

samples/Swift/section-79.swift

@@ -0,0 +1,9 @@
+extension Int: ExampleProtocol {
+    var simpleDescription: String {
+        return "The number \(self)"
+    }
+    mutating func adjust() {
+        self += 42
+    }
+ }
+7.simpleDescription