Update maildrop link

Maildrop moved to gitlab, so here's the updated the url.

README.md

@@ -323,7 +323,7 @@ _MTAs / SMTP servers_
 - [Exim](https://www.exim.org/) - Message transfer agent (MTA) developed at the University of Cambridge. ([Source Code](http://git.exim.org/exim.git)) `GPL-3.0` `C`
 - [Haraka](http://haraka.github.io/) - High-performance, pluginable SMTP server written in Javascript. ([Source Code](https://github.com/haraka/Haraka)) `MIT` `Javascript`
 - [MailCatcher](http://mailcatcher.me/) - Ruby gem that deploys a simply SMTP MTA gateway that accepts all mail and displays in web interface. Useful for debugging or development. ([Source Code](https://github.com/sj26/mailcatcher)) `MIT` `Ruby`
-- [Maildrop](https://github.com/m242/maildrop) - Disposable email SMTP server, also useful for development. `MIT` `Scala`
+- [Maildrop](https://gitlab.com/markbeeson/maildrop) - Disposable email SMTP server, also useful for development. `MIT` `Scala`
 - [MailHog](https://github.com/mailhog/MailHog) - Small Golang executable which runs an SMTP MTA gateway that accepts all mail and displays in web interface. Useful for debugging or development. `MIT` `Go`
 - [OpenSMTPD](https://opensmtpd.org/) - Secure SMTP server implementation from the OpenBSD project. ([Source Code](http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.sbin/smtpd/)) `ISC` `C`
 - [Postfix](http://www.postfix.org/) - Fast, easy to administer, and secure Sendmail replacement. `IPL-1.0` `C`