Merge pull request #492 from boonedox/bugfix/case-classes-typo

fix typo in case classes documentation

Author: heathermiller

tutorials/tour/case-classes.md

@@ -43,7 +43,7 @@ will print
     Var(x) == Var(x) => true
     Var(x) == Var(y) => false
 
-It makes only sense to define case classes if pattern matching is used to decompose data structures. The following [object](singleton-objects.html) defines a pretty printer function for our lambda calculus representation:
+It only makes sense to define case classes if pattern matching is used to decompose data structures. The following [object](singleton-objects.html) defines a pretty printer function for our lambda calculus representation:
 
     object TermTest extends scala.App {
       def printTerm(term: Term) {