Delete unused CSS files (deprecated since Bootstrap 3)
Move/rename javascript files to ease the introduction of web workers
Upgrade jQuery library, and use its development version to ease debugging
Use a Web Worker to encapsulate bzip2 decoding.
It keeps the user interface responsive,  and gives a better feedback to the user :
Withour a Web Worker, the spinner was blocked during decompression, which was misleading for : did my application hang?
Now the spinner keeps turning.
Anyway, the way Web Workers are designed forces us to pass the in/out parameters by copy. So the input byte array and the output string are cloned, which gives an overhead measured around 14% on my computer
Fixes #5
For the unit tests to keep working, I had to move tests.html at the same level as index.html (because the webworker is created in archive.js, by giving the path to its js file. So this path cannot be different between these html files)