dnscrypt-proxy instructions for Ubuntu Linux

As of 2018, you may refer to these instructions for dnscrypt-proxy for Ubuntu Linux:

https://github.com/jedisct1/dnscrypt-proxy/wiki/Installation-Debian-Ubuntu

The link to its parent page (for Linux) is:

https://github.com/jedisct1/dnscrypt-proxy/wiki/Installation-linux

The link to the main page of the wiki (for dnscrypt-proxy) is:

https://github.com/jedisct1/dnscrypt-proxy/wiki