Significant re-engineering of file processing code

* Fully implement file chunking/process files chunk by chunk to
minimize RAM usage (#2)
* Fixed mistakenly using big-endian byte arrays instead of
little-endian for headerLength bytes.
* We no longer need web workers for anything, surprisingly, all of them
have been removed.
* Other small improvements to file processing.
Merge pull request #95 from giuscri/master

Managing overflow of progressBar due to percentages greater than 100%.
Update TweetNacL
Fix manifest
miniLock 1.0

- Initial release.
Update README
Fix image
Tidy up credits section
Shrinking margin-top of div.unlock such there's enough room for div.unlockInfo

Fix #99