Update the draft

[pmeenan]

This makes a bunch of updates and hopefully simplifies the proposal. You can see a live version of it here:

• Added a TL;DR summary at the top with the meat of the details
• Collapsed the 2 different use cases into a single delta compression with a separate "fetch" mechanism for the dynamic case
• Separated out transport and browser-specific concerns
• Switched the stand-alone dictionary fetch to use a link tag/header with a new rel type instead of a custom header
• Added examples for two of the common cases as well as sequence diagrams
• Added a section on the interop issues to consider for caches/CDN's (or anything else in the path)

The one thing that comes to mind that I haven't addressed yet is explicitly purging of existing dictionaries (#3)

Fixes #4 Fixes #5 Fixes #1

[pmeenan]

Thanks. Applied most of the suggestions and added non-opaque language to the flows. Had questions about the "omit" language and the same-origin requirement for dynamic resources.