[author] Add xlsx 0.4.3

xlsx.js grabbed from tag v0.4.3:
https://github.com/SheetJS/js-xlsx/blob/v0.4.3/xlsx.js

Minified version generated using uglifyjs 2.4.12:
$ uglifyjs xlsx.js > xlsx.min.js
Merge pull request #2590 from SheetJS/master

[author] Add xlsx 0.4.3