Fix three typos

Author: hohguy

topics/about_functions_and_closure.js

@@ -3,7 +3,7 @@ module("About Functions And Closure (topics/about_functions_and_closure.js)");
 test("defining functions directly", function() {
     var result = "a";
     function changeResult() {
-        // the ability to access a variables defined in the same scope as the function is known as 'closure'
+        // the ability to access variables defined in the same scope as the function is known as 'closure'
         result = "b";
     };
     changeResult();
@@ -52,9 +52,9 @@ test("using call to invoke function",function(){
     };
 
     //another way to invoke a function is to use the call function which allows 
-    //you to set the callers "this" context.  Call can take any number of arguments: 
+    //you to set the caller's "this" context.  Call can take any number of arguments: 
     //the first one is always the context that this should be set to in the called
-    //function, and the arguments to be sent to the function,multiple arguments are separated by commas.
+    //function, and the arguments to be sent to the function, multiple arguments are separated by commas.
     var result = invokee.call("I am this!", "Where did it come from?");
 
     equal(__, result, "what will the value of invokee's this be?");