Download the javadoc for gson as well

Signed-off-by: Chris Cromer <chris@cromer.cl>

build.gradle

@@ -14,6 +14,7 @@
  */
 
 plugins {
+    id 'idea'
     id 'java'
     id 'application'
     id 'distribution'
@@ -31,6 +32,13 @@ targetCompatibility = 1.8
 applicationName = 'Azaraka'
 mainClassName = 'cl.cromer.azaraka.Azaraka'
 
+idea {
+    module {
+        downloadJavadoc = true
+        downloadSources = true
+    }
+}
+
 repositories {
     mavenCentral()
 }