UINT16 image support

[rqi14]

Hi. I tried the demo with an uint16 grey scale image and it crashed.

tiff.min.js:102 Uncaught abort({}) at Error
at wf (http://seikichi.github.io/tiff.js/tiff.min.js:89:367)
at Vc (http://seikichi.github.io/tiff.js/tiff.min.js:101:412)
at ___syscall192 (http://seikichi.github.io/tiff.js/tiff.min.js:1066:155)
at Li (http://seikichi.github.io/tiff.js/tiff.min.js:1575:41)
at Array.Aa (http://seikichi.github.io/tiff.js/tiff.min.js:1981:431)
at rd (http://seikichi.github.io/tiff.js/tiff.min.js:1146:252)
at _TIFFOpen (http://seikichi.github.io/tiff.js/tiff.min.js:3166:490)
at Object.Yh [as ccall] (http://seikichi.github.io/tiff.js/tiff.min.js:112:19)
at new Lb (http://seikichi.github.io/tiff.js/tiff.min.js:3183:87)
at FileReader. (http://seikichi.github.io/tiff.js/upload.html:47:20)
If this abort() is unexpected, build with -s ASSERTIONS=1 which can give more information.

[rqi14]

Sorry it's just the image is too large