Fixed https://github.com/couchbase/couchbase-lite-java/issues/93 by specifying JDK 1.6 for java core which is common library.

Author: hideki

build.gradle

@@ -3,7 +3,8 @@ apply plugin: 'maven'
 
 version = System.getenv("MAVEN_UPLOAD_VERSION")
 
-sourceCompatibility = 1.6
+sourceCompatibility = JavaVersion.VERSION_1_6
+targetCompatibility = JavaVersion.VERSION_1_6
 
 repositories {
     mavenLocal()