Make it explicit that we're using 1.6

Can be bumped to 1.7 if minsdk is bumped to 8

build.gradle

@@ -77,6 +77,11 @@ android {
 	compileSdkVersion 19
 	buildToolsVersion toolVersion
 
+	compileOptions {
+		sourceCompatibility = "1.6"
+		targetCompatibility = "1.6"
+	}
+
 	sourceSets {
 		main {
 			manifest.srcFile 'AndroidManifest.xml'

project.properties

@@ -1,6 +1,8 @@
 proguard.config=${sdk.dir}/tools/proguard/proguard-android.txt:proguard-project.txt
 
 target=android-19
+compile.source=1.6
+compile.target=1.6
 
 android.library.reference.1=extern/UniversalImageLoader/library
 android.library.reference.2=extern/MemorizingTrustManager