screenshot to PNG files by default

spec/unit/filemanager_spec.lua

@@ -0,0 +1,13 @@
+require("commonrequire")
+local FileManager = require("apps/filemanager/filemanager")
+local UIManager = require("ui/uimanager")
+local Screen = require("device").screen
+local DEBUG = require("dbg")
+
+describe("FileManager module", function()
+    it("should show file manager", function()
+        FileManager:showFiles("../../test")
+        UIManager:scheduleIn(1, function() UIManager:quit() end)
+        UIManager:run()
+    end)
+end)