Add flaskbb (#685)

* Add flaskbb

* Remove excess tag

README.md

@@ -301,6 +301,7 @@ _Mass mailing software - one message to many recipients_
   * [Discourse](http://www.discourse.org/) - Advanced forum / community solution based on Ruby and JS. ([Source Code](https://github.com/discourse/discourse)) `GPLv2` `Ruby`
   * [Elgg](https://elgg.org/) - A powerful open source social networking engine. ([Source Code](https://github.com/Elgg/Elgg)) `GPLv2` `PHP`
   * [Flarum](http://flarum.org) - Delightfully simple forums. Flarum is the next-generation forum software that makes online discussion fun again. ([Source Code](https://github.com/flarum/flarum)) `MIT` `PHP`
+  * [flaskbb](https://flaskbb.org/) - FlaskBB is forum software written in Python using the microframework Flask. You can easily create new topics, posts and send other users private messages. It also includes basic administration and moderation tools. ([Source Code](https://github.com/sh4nks/flaskbb)) `BSD` `Python`
   * [FluxBB](http://fluxbb.org/) - Fast, light, user-friendly forum software for your website. ([Source Code](https://github.com/fluxbb/fluxbb)) `GPLv2` `PHP`
   * [Friendica](http://friendica.com/) - Social Communication Server. ([Source Code](https://github.com/friendica/friendica)) `AGPLv3`
   * [GNU social](https://gnu.io/social/) - Social communication software for both public and private communications. ([Source Code](https://git.gnu.io/gnu/gnu-social)) `AGPLv3` `PHP`