Fail to take regular element screenshot via Safari/Mac #105

When I use this line of code with safari

Shutterbug.shootElement(driver, elementLocator, CaptureElement.VIEWPORT, true);

the result is the below exception whereas I chose a VIEWPORT image that should have no scrolling

`java.lang.UnsupportedOperationException: Full scrollable element screenshot is supported in Chrome, Firefox and MicrosoftEdge browsers only.

at com.assertthat.selenium_shutterbug.utils.web.Browser.takeFullPageElementScreenshot(Browser.java:184)
at com.assertthat.selenium_shutterbug.utils.web.Browser.takeElementViewportScreenshot(Browser.java:657)
at com.assertthat.selenium_shutterbug.core.Shutterbug.shootElement(Shutterbug.java:295)`

the issue is traced to this line of code

BufferedImage image = takeFullPageElementScreenshot();

which should be changed to

BufferedImage image = takeScreenshot();