Update the AutoValue snapshot version from 1.5-SNAPSHOT to 1.6-SNAPSHOT. This should have been done when 1.5 was released.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=169493872
diff --git a/value/pom.xml b/value/pom.xml
index fa2a0e3..da9efa6 100644
--- a/value/pom.xml
+++ b/value/pom.xml
@@ -26,7 +26,7 @@
 
   <groupId>com.google.auto.value</groupId>
   <artifactId>auto-value</artifactId>
-  <version>1.5-SNAPSHOT</version>
+  <version>1.6-SNAPSHOT</version>
   <name>AutoValue</name>
   <description>
     Immutable value-type code generation for Java 1.6+.