Support the insertion of 0

I use btree-js when debugging my C++ btree code to make sure everything is operating correctly and 0 is a number in my current testing model

Author: CheyenneForbes

assets/js/btree-node.js

@@ -30,8 +30,9 @@ BTreeNode.prototype.traverse = function(value, strict) {
 
 BTreeNode.prototype.insert = function(value){
 
-  var int = parseInt(value) || 0;
-  if ( int <= 0 || int > 1000000000000 ) {
+  var int = parseInt(value);
+
+  if ( typeof value !== "number" || int > 1000000000000 ) {
     alert('Please enter a valid integer.');
     return false;
   }