refactor(regexp): ensure options are alphabetically sorted

Author: mbroadst

lib/bson/regexp.js

@@ -1,4 +1,12 @@
 'use strict';
+
+function alphabetize(str) {
+  return str
+    .split('')
+    .sort()
+    .join('');
+}
+
 /**
  * A class representation of the BSON RegExp type.
  *
@@ -11,7 +19,7 @@ function BSONRegExp(pattern, options) {
   // Execute
   this._bsontype = 'BSONRegExp';
   this.pattern = pattern || '';
-  this.options = options || '';
+  this.options = options ? alphabetize(options) : '';
 
   // Validate options
   for (var i = 0; i < this.options.length; i++) {