Target Java 7.

Java 6 was EOL'd in March, 2013. Java 7's last public update was in
April, 2015. If a company is not running Java 7 (at least! it seems
as if they'll never update. Embrace the past: target Java 7.

.buckconfig

@@ -1,5 +1,7 @@
 [java]
   src_roots = /java/client/src, /java/client/test, /java/server/src, /java/server/test
+  source_level = 7
+  target_level = 7
 
 [project]
   ignore = \

rake-tasks/crazy_fun/mappings/java.rb

@@ -318,8 +318,8 @@ def handle(fun, dir, args)
             :optimize             => true,
             :debug                => true,
             :nowarn               => true,
-            :source               => '1.6',
-            :target               => '1.6'
+            :source               => '1.7',
+            :target               => '1.7'
           ) { |ant|
             ant.classpath(:refid => "#{args[:name]}.path")