disable predexing on travis

.travis.yml

@@ -16,4 +16,4 @@ android:
   licenses:
     - '.+'
 script:
-    - ./gradlew assembleFreeRelease
+    - ./gradlew assembleFreeRelease -PdisablePreDex

build.gradle

@@ -106,6 +106,14 @@ android {
             }
 
         }
+
+        project.plugins.whenPluginAdded { plugin ->
+            if ("com.android.build.gradle.AppPlugin".equals(plugin.class.name)) {
+                project.android.dexOptions.preDexLibraries = !project.hasProperty('disablePreDex')
+            } else if ("com.android.build.gradle.LibraryPlugin".equals(plugin.class.name)) {
+                project.android.dexOptions.preDexLibraries = !project.hasProperty('disablePreDex')
+            }
+        }
     }
 
     packagingOptions {