avoid redeclaration of proguard files, prevents future #3127

// FREEBIE

build.gradle

@@ -180,19 +180,7 @@ android {
         }
         release {
             minifyEnabled true
-            proguardFiles getDefaultProguardFile('proguard-android.txt'),
-                          'proguard-google-play-services.pro',
-                          'proguard-dagger.pro',
-                          'proguard-jackson.pro',
-                          'proguard-sqlite.pro',
-                          'proguard-appcompat-v7.pro',
-                          'proguard-square-okhttp.pro',
-                          'proguard-square-okio.pro',
-                          'proguard-spongycastle.pro',
-                          'proguard-rounded-image-view.pro',
-                          'proguard-glide.pro',
-                          'proguard-shortcutbadger.pro',
-                          'proguard.cfg'
+            proguardFiles = buildTypes.debug.proguardFiles
             signingConfig signingConfigs.release
         }
         testing.initWith(buildTypes.debug)