Add mvn install in Readme

Change-Id: I4777f4ebe1f345024c38c4c0378b7b905daf03c1
diff --git a/Readme.md b/Readme.md
index d05b539..1860e48 100644
--- a/Readme.md
+++ b/Readme.md
@@ -67,6 +67,12 @@
 $ mvn clean test
 ```
 
+To build a Krill library and install it in your local Maven repository
+(needed for Kustvakt) ...
+
+```
+$ mvn install
+```
 ## Caveats
 
 Krill operates on tokens and is limited to a single tokenization stream.