Add Mailpile, fixes #141

Import software from https://github.com/juandecarrion/awesome-self-hosted
Other software was already present here or on awesome-sysadmin

README.md

@@ -122,6 +122,7 @@ See also [Static Site Generators](#static-site-generators) and  [Content Managem
 ### Email
   * [Cypht](http://cypht.org/index.html) - A feed reader for your email accounts - `GPL` 
   * [mailcow](https://github.com/andryyy/mailcow) - Mail server suite based on Dovecot, Postfix and other open source software, that provides a modern Web UI for administration. `GPL`
+  * [Mailpile](https://www.mailpile.is/) - Webmail client with search, filtering, encryption features and more ([Source code](https://github.com/mailpile/Mailpile)) `AGPLv3` `Python`
   * [RainLoop](http://www.rainloop.net/) - Simple, modern & fast web-based email client. ([Demo](http://demo.rainloop.net/), [Source code](https://github.com/RainLoop/rainloop-webmail)). `AGPLv3` `PHP`
   * [Roundcube](https://roundcube.net) - A web interface to act as an IMAP frontend ([Screenshots](https://roundcube.net/screens/)) ([Source code](https://github.com/roundcube/roundcubemail/)) `GPLv3` `PHP`