Update cartodb-postgresql install info (including upgrade)

README.md

@@ -52,7 +52,7 @@ and code.
 
   - Ubuntu 12.04
   - Postgres 9.3.x (with plpythonu extension)
-  - cartodb-postgresql 0.2.0+
+  - cartodb-postgresql 0.2.1
   - Redis 2.2+
   - Ruby 1.9.3
   - NodeJS 0.8.x

UPGRADE

@@ -17,7 +17,12 @@ Unless stated otherwise, assume any new CartoDB release requires calling these c
 Mandatory migration
 -------------------
 
-Versions marked at the NEWS.md as requiring this migration must run all this commands:
+Versions marked at the NEWS.md as requiring this migration must:
+
+ - ensure the required version of cartodb-postgresql extension
+   (see README.md) is installed on the user database hosts
+
+ - run all this commands:
 
  $ bundle exec rake db:migrate
  $ bundle exec rake cartodb:db:reset_trigger_check_quota