Do not assume "postgres" user exists

Revert "CDB-3079 enforces postgres user in preparation script"
Revert "CDB-3079 enforces postgres user in preparation script"
[TRAVIS] set "postgres" user for running tests (using PGUSER)

Closes #152
Stubs next version
Upgrades dependencies
Change expected error code for backend crash. cartodb-psql 0.4.0
returns 500 error when it's not possible to connect to PostgreSQL.
New header for database host serving the request
Merge pull request #173 from CartoDB/CDB-3656

New header for database host serving the request
Corrects JSDoc
Health check endpoint
Call check before callback so the server is closed before the callback
throws an exception
Make check() before any other assert
Adds extra information when status/headers dont match
DRY
Proper db params object
Merge pull request #174 from CartoDB/CDB-3692

Health check endpoint
Removes unused method in assert extension
Returns 401 Unauthorized for queries without permission
Update API.md
Fixes tests related to send 401 status code for unauthorized requests
Upgrades cartodb-redis and re-generates npm-shrinkwrap.json
Release 1.17.0