OSX: fix for doubleclick and dragging

[HesselM]

These 4 commits solve the following issues:

General:
2dede35: enables calling multiple dragRel functions with small and large dx/dy in sequence. Previously, dragging lost track when using multiple calls as the OS could not follow the speed.

OSX
dce333d: added 0.01 delay for the OS to catch up in _dragTo. (similar to _moveTo)
a655757 and 14e2ad0 : fixed multi-click support by adding a new function. The calls to 'doubleClick' and 'tripleClick' now function as expected. 'click' with 'click=' just executes single clicks.

This PR fixes issue #71

Edit: As noted at several places, the window in which a double click should be performed has to be active/in-focus! So, in order to use a double click properly:

1. Focus window
2. Perform double/multi click in this window

[asweigart]

Sorry for the delays on this. I'll have access to a mac laptop to test these changes tonight. Thanks!

[HesselM]

$ git clone https://github.com/asweigart/pyautogui.git
$ cd pyautogui
$ git config --local user.name "name"
$ git config --local user.email "email"
$ git remote add osxfix https://github.com/HesselM/pyautogui.git
$ git fetch osxfix 
$ git rebase master osxfix/master

(from http://stackoverflow.com/questions/6022302/how-to-apply-unmerged-upstream-pull-requests-from-other-forks-into-my-fork )

Edit> If you want to use the double click, make sure you first select the window in which the double click should be performed. If the window is not (yet) active, it will not function.

[ibrr1]

Still not working for me! Even though I am selecting the window where i want to double click!

[afs2015]

Tested doubleClick() using http://unixpapa.com/js/testmouse.html on my Mac running Sierra 10.12.6 and it appeared to work fine.

[specialak]

pyautogui.moveTo(203,668) and pyautogui.click(x = 203,y = 668) are also not working on high Sierra but pyautogui.position() is working well. Is anyone here to help me??
thanks,