test is correct and working

In Selenium 2.53.1 (latest 2.x) the test does not pass, for some reasons, button up event is not fired.

see 38c6ef7 debug output:

Drop here, mouseover, mouseover, mouseover, mousemove, mousemove, mousemove, mousedown, mousedown,
mousedown, mouseout, mouseout, mouseout, mouseover, mouseover, mouseover, mouseover

In Selenium 3.x it passes.

Drop here, mouseout, mouseover, ..., mouseup, Dropped small!, click, click, dblclick, dblclick, mouseout,
mouseout, mouseout, mouseout, mouseover, mouseover, mouseover

notice no mouseup nor Dropped small! in Selenium 2.53.1 browser event/debug log

Selenium 2.53.1 is very old and the test should be skipped in minkphp/MinkSelenium2Driver#359 and then tested in minkphp/MinkSelenium2Driver#354

@stof please merge this test as requested in minkphp/MinkSelenium2Driver#359 (comment)

test can be tested locally by clicking the smaller box - notice the drag and drop works even without any mouse move and also when you hold the mouse, the box is not visible

I will then take care of skipping the test for Selenium 2.53.1 and testing with 3.x.

@stof this is the test you requested in minkphp/MinkSelenium2Driver#359 (comment), can you please review it and merge?