Change annotation create response to 201

With the URL to read the annotation in a Location header
Send 403 when authenticated but not authorized
Merge pull request #96 from seanh/63-improve-response-codes-and-headers

#63 improve response codes and headers
search: Allow searching over empty indices

We must specify 'allow_unmapped' in the sort directives for these
queries, because otherwise elasticsearch will claim the fields are
unmapped when the indices are empty -- even if the mapping contains
entries for the 'updated' field.
tox: Fix tox config typo introduced by 0176afd0
dist: Add manifest file

We need CHANGES.rst to be included in the distribution otherwise
setup.py will bomb.
tests: Install testing deps with tox
Search using a match query rather than term filter
Only add match_all to query when needed
Document HOST and PORT environment variables

Close #99
Merge pull request #89 from Treora/change_term_match

Change term filter into match query
Add instructions to readme about Flask dependency
Merge pull request #100 from Treora/update_readme

Add instructions to readme about Flask dependency
Update tox.ini

Add flask extras
Update README.rst

Use testing extras to bootstrap testing.
Remove orphaned method
Fix RuntimeError on failing authz filter
Have search call search_raw
Have count call search
Fix Document test to use new search call signature