fixes broken links pointing to diveintomark.org, in detect.html

The detect.html (Chapter: 02. Detecting HTML5 Features) has links
pointing to the diveintomark.org domain, which has expired. To fix
this, all links from diveintomark.org were replaced with a
corresponding link of the Internet Archive's snapshot of respective
the page.
fixes a broken link pointing to en.flossmanuals.net, in video.html
(Chapter: 05. Video on the Web).

en.flossmanuals.net had changed the URL of the page which describes
'Two-Pass Encoding' in ffmpeg2theora, this fix, links to the new
location of the page.
replaces old links to iso.org with the canonical links, in extensibility.html
(Chapter: 10. `Distributed,' `Extensibility,' & Other Fancy Words).

iso.org has updated their site and have a new URL to the 'date and time format page.
Merge pull request #59 from r5d/links-fix

Links fix (Chapters. 02, 05 & 10)