Fix Windows spec by using element_dimension instead of normal

* interestingly on Windows it seems like there are margins there..
  for some reason
* I dare you travis to fail me now!
Rounding font data height as Windows creats 15.75 when asked for 16

* #joyofguiprogramming #joyofcrossplatform #weneedawindowsdev
Merge pull request #916 from shoes/fix-windows-specs

Fix Windows spec by using element_dimension instead of normal + font cache adjustments