Add Red Moon to the tools category

Author: raatmarien

categories/tools.md

@@ -127,6 +127,7 @@ App Name                   | Describe                  | Major Language
 App Name                   | Describe                  | Major Language             | Download 
 :------------------------: | :------------------------ | :------------------------: | :------------------------: 
 [RxWeather](https://github.com/SmartDengg/RxWeather) | Weather app with architecting Android with RxJava | Java |  
+[Red Moon](https://github.com/raatmarien/red-moon) | A feature rich screen filter app | Java | [![Get it on Google Play](http://i.imgur.com/7sq06lr.png)](https://play.google.com/store/apps/details?id=com.jmstudios.redmoon)
 
 ###S
 App Name                   | Describe                  | Major Language             | Download