Build with Java 8

Change-Id: I3550cc606949556520875298c7371a067f5a270e

.buckconfig

diff --git a/.buckconfig b/.buckconfig
index 2b818b6..275ec6a 100644
--- a/.buckconfig
+++ b/.buckconfig
@@ -6,7 +6,8 @@
 [java]
   jar_spool_mode = direct_to_jar
   src_roots = java, resources
-
+  source_level = 8
+  target_level = 8
 [project]
   ignore = .git, eclipse-out/
   parallel_parsing = true