gradle: Enable java 8 language feature support

References:
- [1]: https://developer.android.com/studio/write/java8-support

Signed-off-by: Aayush Gupta <theimpulson@e.email>

app/build.gradle

@@ -37,7 +37,13 @@ android {
     aaptOptions{
         additionalParameters '-I', 'app/e-ui-sdk.jar'
     }
-
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+    kotlinOptions {
+        jvmTarget = '1.8'
+    }
 }
 
 dependencies {