change M12 to M13 + gradle plugins to 0.12.4

Author: Konstantinos Chalkias

README.md

@@ -80,9 +80,9 @@ Change directories to the newly cloned repo:
 
      cd cordapp-tutorial
      
-Check out the latest milestone release tag (currently `release-M12.1`):
+Check out the latest milestone release tag (currently `release-M13`):
 
-     git checkout -b [your-branch-name] release-M12.1
+     git checkout -b [your-branch-name] release-M13
      
 Non-milestone releases are development branches, and can be unstable 
 or even broken. You should develop against a milestone release.

build.gradle

@@ -1,6 +1,6 @@
 buildscript {
-    ext.corda_release_version = '0.13-SNAPSHOT'
-    ext.corda_gradle_plugins_version = '0.11.2'
+    ext.corda_release_version = '0.13.0'
+    ext.corda_gradle_plugins_version = '0.12.4'
     ext.kotlin_version = '1.1.2'
     ext.quasar_version = '0.7.6'
     ext.junit_version = '4.12'