Misc cleanup and name changes
read_box_header() and read_int() functions
Parsing manifest and bootstrap info to get fragment numbering

This is based on looking at KSV’s AdobeHDS.php script
Update fraction complete based on fragment number
HDS: Get rid of the URL and pvtoken printouts
Move resuming-empty-file workaround out of wrapper to higher level

Also, the os.path.isfile() check doesn’t seem to be necessary.
Merge branch 'hds'
Update readme a bit to compensate for different streaming servers
Attempt at a helpful message when GTK package missing