Added global theme attribute for list item color (with default adapter implementation).

library/src/main/java/com/afollestad/materialdialogs/MaterialDialog.java

@@ -1116,7 +1116,7 @@ public class MaterialDialog extends DialogBase implements View.OnClickListener,
 
         public MaterialDialogAdapter(Context context, int resource, int textViewResourceId, CharSequence[] objects) {
             super(context, resource, textViewResourceId, objects);
-            final int fallback = DialogUtils.resolveColor(getContext(), android.R.attr.textColorSecondary);
+            final int fallback = DialogUtils.resolveColor(context, android.R.attr.textColorSecondary);
             itemColor = DialogUtils.resolveColor(getContext(), R.attr.md_item_color, fallback);
         }