Merge pull request #841 from Neilpang/master

gitter

README.md

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 # An ACME Shell script: acme.sh [![Build Status](https://travis-ci.org/Neilpang/acme.sh.svg?branch=master)](https://travis-ci.org/Neilpang/acme.sh)
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+[![Join the chat at https://gitter.im/acme-sh/Lobby](https://badges.gitter.im/acme-sh/Lobby.svg)](https://gitter.im/acme-sh/Lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 - An ACME protocol client written purely in Shell (Unix shell) language.
 - Full ACME protocol implementation.
 - Simple, powerful and very easy to use. You only need 3 minutes to learn it.