Upgrade gradle from 3.0.1 to 3.1.4

lib/android/build.gradle

@@ -8,7 +8,7 @@ buildscript {
         jcenter()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.0.1'
+        classpath 'com.android.tools.build:gradle:3.1.4'
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files