feat(ext-json): export EJSON at top level of module

Author: mbroadst

Diff for: lib/bson.js

@@ -16,6 +16,7 @@ const MaxKey = require('./max_key');
 const DBRef = require('./db_ref');
 const Binary = require('./binary');
 const constants = require('./constants');
+const EJSON = require('./extended_json');
 
 // Parts of the parser
 const internalDeserialize = require('./parser/deserializer');
@@ -234,5 +235,8 @@ module.exports = Object.assign({}, constants, {
   setInternalBufferSize,
 
   // legacy support
-  ObjectID: ObjectId
+  ObjectID: ObjectId,
+
+  // Extended JSON
+  EJSON
 });