Adds basic support for the Swift programming language

Text only lexer for now until Pygments catches up

samples/Swift/section-61.swift

@@ -0,0 +1,8 @@
+class Counter {
+    var count: Int = 0
+    func incrementBy(amount: Int, numberOfTimes times: Int) {
+        count += amount * times
+    }
+}
+var counter = Counter()
+counter.incrementBy(2, numberOfTimes: 7)