Flesh out room alias section.
Merge pull request #6 from matrix-org/paul/doc

Clarify how m.room.alias event works
More spec work.
swagger: Added DELETE method for directory server.
Add information about the initialSync API.

Outline and describe the keys from the initial sync API. Hide room-scoped
initial sync API for now as it is not implemented and needs more thought before
it can be specced.
Clarify room permission / power level information.
Add more section headings.
Update JSFiddles/how-to to support the new registration format.
Clarify how-to some more.
Add quick and dirty doc about state resolution
SPEC-3: First hack at defining some of the various event related concepts
Clarify that room alias domain names will be server-scoped; nonlocal edits are unliekly to work but nonlocal lookups will