JavaScript implementation for Vert.x js-lang

This is the first commit. Currently the following features are
supported:

Protocols:
- Binary protocol
- Compact protocol
- JSON protocol
- Multiplexed

Transports:
- Vert.x EventBus
Update the js generator to support Vert.x

Add a new switch --gen js:vertx to generate source for Vert.x js-lang
Fix a defect in protocol.js

JavaScript supports only numeric doubles, therefore the largest integer
value which can be represented in JavaScript is +/-2^53. Currently I64
integer is not supported precisely.
change README.md
Add tutorial projects for vert.x js
Merge branch 'thrift-for-vertx-js' into thrift-for-vertx