add TravisCI badge although it is not valid yet
# mruby/c
+[![Build Status](https://travis-ci.com/mrubyc/mrubyc.svg?branch=master)](https://travis-ci.com/mrubyc/mrubyc)
+
[![Join the chat at https://gitter.im/mrubyc/mrubyc](https://badges.gitter.im/mrubyc/mrubyc.svg)](https://gitter.im/mrubyc/mrubyc?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
mruby/c is an another implementation of mruby.
