add return_terms, stream, and continuation elements to RpbIndexReq
Test for object existence using head request.

Use the PB head option or an HTTP HEAD request.
start 2i specs
pass a couple specs
more specs
implement naïve key & value fetches
spec out keys and values operations
initialization
IndexCollection implementation
Less 2i fail
Use IndexCollection instead of a json-parsed array
fix a filename
spec out return_terms from the query side
add a next_page method
Add some documentation on IndexCollection.
Add 1.4 2i fields to RpbIndexResp
Support query_options in protobufs
Refactor IndexCollection to support initialization both from json and decoded protobuffs
Memoize values retrieval
Beefcake should use IndexCollection for index responses