[#39] pgsql dep. Initial pgsql backend.
Merge branch 'jfacorro.39.pgsql.support' into jfacorro.39.pgsql.backend.and.store
[#39] Use mixin for testing sumo_docs. Add pgsql backend and store.
[#39] pgsql create schema.
[#39] WIP. Find command with Postgres.
[#39] Adapted WHERE clause generator to handle numbered slots.
[#39] pgsql delete_by.
[#39] Removed lager:info.
Merge pull request #101 from inaka/jfacorro.39.pgsql.backend.and.store

[#39] pgsql backend and store