error on headerString[key].split(2,/:/) (#41)

* error on headerString[key].split(2,/:/)
the last argument of array is a function, you can not do split on function
i have added if(typeof headerString[key] != 'function') to fix it

* Update ofx.js

Author: marcosmoski

lib/ofx.js

@@ -161,7 +161,9 @@ OFX.parse = function (ofxStr, fn) {
   data.header = {};
 
   for(var key in headerString){
-    var headAttributes = headerString[key].split(/:/,2);
+    if (typeof headerString[key] === "string"){
+      var headAttributes = headerString[key].split(/:/,2);
+    }
     if (headAttributes[0]) data.header[headAttributes[0]] = headAttributes[1];
   }
   fn(data);