Eliminate global var leak.

Mocha is picking this up in our test suite as a leaked global var.

lib/api/index.js

@@ -15,7 +15,7 @@ var api = {
 };
 
 module.exports = function(obj){
-    for(key in api){
+    for(var key in api){
         obj[key] = api[key];
     }
 };