Update readme to include scala 2.12

Author: kx79wq

README.md

@@ -3,9 +3,9 @@ Scala implementation of Histogrammar
 
 [![DOI](https://zenodo.org/badge/doi/10.5281/zenodo.61344.svg)](http://dx.doi.org/10.5281/zenodo.61344)
 
-See [histogrammar.org](http://histogrammar.org) for a complete introduction to Histogrammar.
+See [https://histogrammar.github.io/histogrammar-docs](https://histogrammar.github.io/histogrammar-docs) for a complete introduction to Histogrammar.
 
-This is a Scala implementation for Scala versions 2.10 and 2.11.
+This is a Scala implementation for Scala versions 2.10, 2.11 and 2.12.
 
 Installation
 ============
@@ -22,6 +22,12 @@ or
 mvn install -P scala-2.11
 ```
 
+or 
+
+```bash
+mvn install -P scala-2.12
+```
+
 in the base directory (to compile everything) or one of the subdirectories. All subdirectories depend on `core`, so this must be installed first.
 
 Status