Have create_publicuser rake task not complain if user already exists

This commit uses the PostgreSQL 9.0+ "DO" construct to only create
the users when they don't exist already. We require 9.1+ already
so no problem about that.
fixed saving previous wrong state CDB-1496
update table after georeference CDB-1497
Added varnish PPA to README.md
Merge branch 'master' of https://github.com/CartoDB/cartodb
fixed specs CDB-1497
Merge branch 'master' of github.com:CartoDB/cartodb
CDB-1362 #resolve Tables, Visualizations, DB sizes reporting

to StatsD.

Note this requires correct config values to be set on app_config.yml.
Look at config/initializers/statsd.rb for them
CDB-1362 #comment Ensure exceptions are rescued in User#update_gauge
CDB-1362 #comment Fix typo
Updated resque startup procedure on README
Updated contributors on README
Use a version-dependent backend killer command in spec helper

Closes #267.
Defines a static User::terminate_database_connections method and
uses it from both user destructor and testsuite
Merge pull request #348 from strk/version-based-backend-killer2

Use a version-dependent backend killer command in spec helper
Reload User model schema on cartodb:db:setup task (fixes #259)

Fixes multiple errors when running cartodb:db:setup without reloading Rails
environment.
Merge pull request #298 from strk/create-user-if-not-exists

Have create_publicuser rake task not complain if user already exists
merged with master