Changes related to using byte-ranges when source is bundled or compiled. Zipped sources now use http.ServeContent() for fancier file delivery (especially for Range requests on large files such as videos).

* add an example to test byte ranges, and output to show that they're happening
* add -verbose messages when Range is being used
* add SelfservingReadSeeker to bundle.go
* change rawFileHandler in webserver.go to use SelfservingReadSeeker and http.ServeContent to deliver from zipped content on Range requests