Fixed image blurring

When position becomes a float the image is blurred. By using parseInt we force it to render properly and might even improve performance according to the article.

See http://www.html5rocks.com/en/tutorials/canvas/performance/#toc-avoid-float
Added radix to prevent issues with parseInt
Merge pull request #217 from splitfeed/patch-1

Fixed image blurring of markers
Merge remote-tracking branch 'flotr2/master'