Revert "tests are failing because of api limits, removed badge from readme"

This reverts commit 76e2f0dc.

README.md

-# letsencrypt.sh
+# letsencrypt.sh [![Build Status](https://travis-ci.org/lukas2511/letsencrypt.sh.svg?branch=master)](https://travis-ci.org/lukas2511/letsencrypt.sh)
 
 This is a client for signing certificates with an ACME-server (currently only provided by letsencrypt) implemented as a relatively simple bash-script.