Revert "remove class based exercises"

This reverts commit 290e7f1da4.

reverseString/reverseString.js

@@ -1,5 +1,5 @@
-var reverseString = function(string) {
-  return string.split('').reverse().join('')
+var reverseString = function() {
+
 }
 
-module.exports = reverseString
+module.exports = reverseString

reverseString/reverseString.spec.js

@@ -5,11 +5,11 @@ describe('Hello World', function() {
     expect(reverseString('hello')).toEqual('olleh');
   });
 
-  it('reverses multiple words', function() {
+  xit('reverses multiple words', function() {
     expect(reverseString('hello there')).toEqual('ereht olleh')
   })
 
-  it('works with numbers and punctuation', function() {
+  xit('works with numbers and punctuation', function() {
     expect(reverseString('123! abc!')).toEqual('!cba !321')
   })
-});
+});