com.github.ben-manes.versions version 0.21.0

* Update unit tests to use it
* Update unit tests to expect updates of versions to update to it (which should make unit tests pass again)
* Update README to use it
* Update README to say that it is supported

README.md

@@ -17,7 +17,7 @@ Include in your `build.gradle`
 ```groovy
 plugins {
   id 'se.patrikerdes.use-latest-versions' version '0.2.8'
-  id 'com.github.ben-manes.versions' version '0.20.0'
+  id 'com.github.ben-manes.versions' version '0.21.0'
 }
 ```
 
@@ -33,7 +33,7 @@ buildscript {
     }
     dependencies {
         classpath "se.patrikerdes:gradle-use-latest-versions-plugin:0.2.8"
-        classpath 'com.github.ben-manes:gradle-versions-plugin:0.20.0'
+        classpath 'com.github.ben-manes:gradle-versions-plugin:0.21.0'
     }
 }
 
@@ -48,7 +48,7 @@ Include in your `build.gradle.kts`
 ```groovy
 plugins {
   id("se.patrikerdes.use-latest-versions") version "0.2.8"
-  id("com.github.ben-manes.versions") version "0.20.0"
+  id("com.github.ben-manes.versions") version "0.21.0"
 }
 ```
 
@@ -64,7 +64,7 @@ buildscript {
     }
     dependencies {
         classpath("gradle.plugin.se.patrikerdes:gradle-use-latest-versions-plugin:0.2.8")
-        classpath("com.github.ben-manes:gradle-versions-plugin:0.20.0")
+        classpath("com.github.ben-manes:gradle-versions-plugin:0.21.0")
     }
 }
 
@@ -116,7 +116,7 @@ variables – and you build.gradle file will look like this:
 ```groovy
 plugins {
     id 'se.patrikerdes.use-latest-versions' version '0.2.8'
-    id 'com.github.ben-manes.versions' version '0.20.0' // <- Updated
+    id 'com.github.ben-manes.versions' version '0.21.0' // <- Updated
 }
 
 apply plugin: 'java'
@@ -251,7 +251,7 @@ dependencies {
 ## Compatibility
 
 **Gradle version:** 2.8 - 4.10.2 (Updating plugin dependencies only work in 4.4+)<br/>
-**Versions Plugin version:** 0.12.0 - 0.20.0<br/>
+**Versions Plugin version:** 0.12.0 - 0.21.0<br/>
 **JDK version:** 7 - 11 (7 is targeted but not tested, 11 is currently not tested but is known to work)
 
 ## Instructions for building this plugin from source

src/test/groovy/se/patrikerdes/CurrentVersions.groovy

@@ -1,7 +1,7 @@
 package se.patrikerdes
 
 class CurrentVersions {
-    public static final String VERSIONS = '0.20.0'
+    public static final String VERSIONS = '0.21.0'
     public static final String JUNIT = '4.13-beta-2'
     public static final String LOG4J = '1.2.17'
 }