* descriptions refactoring

Author: adamnemecek

Sources/RedBlackTree.swift

@@ -75,15 +75,7 @@ public struct RedBlackTree<Key: Comparable, Value>: Probable, Collection, Custom
 		- returns:	String
 	*/
 	public var description: String {
-        var output = "["
-        let l = count - 1
-        for i in 0..<count {
-            output += "\(self[i])"
-            if i != l {
-                output += ", "
-            }
-        }
-        return output + "]"
+        return "[" + map { "\($0)" }.joined(separator: ", ") + "]"
 	}
 
 	/**

Sources/SortedMultiSet.swift

@@ -72,15 +72,7 @@ public struct SortedMultiSet<T: Comparable>: Probable, Collection, Equatable, Cu
 		- returns:	String
 	*/
 	public var description: String {
-		var output = "["
-		let l = count - 1
-		for i in 0..<count {
-			output += "\(self[i])"
-			if i != l {
-				output += ", "
-			}
-		}
-		return output + "]"
+    return "[" + map { "\($0)" }.joined(separator: ", ") + "]"
 	}
 
 	/**