Make canvas transform matrix account for devicePixelRatio
Fix invalid version number in truetype 'head' table
Sanitization of truetype fonts to fix #2537
Merge pull request #2584 from mduan/issue2537

Add sanitization of truetype fonts to fix #2531 and #2537
Merge pull request #2572 from mduan/issue2477

Make canvas transform matrix account for devicePixelRatio