add gitter badge

smells like teen spirit

README.md

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+[![Join the chat at https://gitter.im/Daplie/letsencrypt-express](https://badges.gitter.im/Daplie/letsencrypt-express.svg)](https://gitter.im/Daplie/letsencrypt-express?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
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 # letsencrypt-hapi
 
 Free SSL and Automatic HTTPS for node.js with hapi.js and other middleware systems via Let's Encrypt