fix($scaling): multiple: false w/ scaling results in stalled uploads
fixes #1278
fix($scaling): invalid batch ID for scaled files
docs($scaling): comments
ref #1278
fix($button): fix input button in IE8 & 7

- height: 100% in IE7 prevents the file input from being clicked.
- if font-size is too large, the file input becomes visible in IE8.

ref #1152
ref #1277