Support for 16bits unsigned images #28

Salut,
There is a problem for loading unsigned 16 bits images ( BITPIX = 16 and BZERO = 32768)
This is the fix to handle them correctly :

in Image.prototype._getFrame :

Line 760:
change
...
case 16:
tmp = new Int16Array(buffer);
...
with
...
case 16:
if(bzero==32768)
tmp = new Uint16Array(buffer);
else
tmp = new Int16Array(buffer);
...

Thanks for your nice work!
Pierre