Preclude adding stub participants as team members. Resolves #2364
Added Community.from_slug method
Added REST API to get community with all its members.
Moved converting participant to JSON to utils.json
Test refactored
whitespace
Merge pull request #2429 from gittip/stub-participants

Preclude adding stub participants as team members
use cls.db instead of passing website.db as argument
move Participant.get_members_of_community() into Community.get_members()
move gittip.utils.json.from_participant() to Participant.to_dict()
don't make costly DB requests by default
whitespace
Bump version to 13.1.4
Bump version to 13.1.4-dev
support the `tippee` argument of `set_tip_to()` being a `Participant`
optimize clear_tips_{giving,receiving}
fix atomicity of clear_tips_{giving,receiving}
update uses of set_tip_to() to give Participant instead of username
Added pagination to community members REST API
rescue from exception on checking card status
log exception to stdout and sentry