Merge branch '2.13'

Author: Tatu Saloranta

guava/README.md

@@ -12,7 +12,7 @@ To use module on Maven-based projects, use following dependency:
 <dependency>
   <groupId>com.fasterxml.jackson.datatype</groupId>
   <artifactId>jackson-datatype-guava</artifactId>
-  <version>2.11.3</version>
+  <version>2.12.1</version>
 </dependency>
 ```
 

guava/pom.xml

@@ -26,6 +26,9 @@ Guava (http://code.google.com/p/guava-libraries/) types (currently mostly just c
   </contributors>
 
   <properties>
+    <!-- In Jackson 2.12 was guava 21
+                    2.13 ... ?
+      -->
     <version.guava>25.1-jre</version.guava>
 
     <!-- 11-Sep-2015, tatu: As per [datatype-guava#80] -->