correct typo
include offsetLeft and offsetTop in x,y calculation

If an element had been placed on the page using css (e.g. 'top: 50px;') then the element would end up offset from the cursor when dragging.
Merge pull request #1 from staygrimm/patch-1

include offsetLeft and offsetTop in x,y calculation
allow option for rounding pixels on move
make example work
round translate pixels by default
set roundPixels to true on initialization
Merge pull request #7 from staygrimm/master

correct typo