update json-ld examples

[tcole3]

Updated json-ld examples and added text describing these examples; Also updated abstract and introduction @BigBlueHat if edits to abstract and introduction don't conflict with your work in progress, please merge.

[tcole3]

Marked as non-substantive for IPR from ash-nazg.

[BigBlueHat]

Rawgit: https://rawgit.com/tcole3/web-annotation/77d0d1b6e068e23eedb92c595e86a17932ef6e21/serialization-html-note/index-respec.html

[BigBlueHat]

@tcole3 there's some good stuff in here, but some things I'd like to undo are:

• text in the intro suggesting that one can only annotate "resources found on the Web"
  • the Model (and friends) are about annotating anything and a means to express those annotation on the Web
• the inclusion of the Web Annotation Protocol mention is a bit distracting (the Note doesn't reference it agian)
• I'd not put the media type in the intro...clutter-y

Otherwise, I think these are good changed.

Also, the addition of the use cases with links to places where they might be used is a great addition. Thank you!

[BigBlueHat]

@tcole3 changes look good, thanks!