removed controversial performance info, fixed recursion info and typos

scala.html.markdown

@@ -231,7 +231,7 @@ r foreach println
 
 (5 to 1 by -1) foreach (println)
 
-// A while loops
+// A while loop
 var i = 0
 while (i < 10) { println("i " + i); i += 1 }
 
@@ -239,17 +239,18 @@ while (i < 10) { println("i " + i); i += 1 }   // Yes, again. What happened? Why
 
 i    // Show the value of i. Note that while is a loop in the classical sense -
      // it executes sequentially while changing the loop variable. while is very
-     // fast, faster that Java loops, but using the combinators and
+     // fast, but using the combinators and comprehensions above is easier
-     // comprehensions above is easier to understand and parallelize
+     // to understand and parallelize
 
-// A do while loop
+// A do-while loop
 i = 0
 do {
   println("i is still less than 10")
   i += 1
 } while (i < 10)
 
-// Tail recursion is an idiomatic way of doing recurring things in Scala.
+// Recursion is the idiomatic way of repeating an action in Scala (as in most
+// other functional languages).
 // Recursive functions need an explicit return type, the compiler can't infer it.
 // Here it's Unit.
 def showNumbersInRange(a: Int, b: Int): Unit = {