2-3000% performance enhancement in IE7

Use an array and not a string to store chunks internally. Increases
performance by 2-3000% in IE7. No measurable  changes in performance in
other browsers.
dynamic keys in getBlock fix
fixed join() to join('')
Removed incorrect fix in unit tests
Merge pull request #253 from jlkonsultab/master

2-3000% performance enhancement in IE7