Postgresql migration

* Change mysql to pg dependency
* Change database.yml
Merge branch 'master' into migrate-to-postgresql
Change travis configuration
Merge branch 'master' into migrate-to-postgresql
Merge branch 'master' into migrate-to-postgresql

* master:
  We want Ruby 1.9 syntax
  new settings
Merge pull request #5 from Soluciones/migrate-to-postgresql

Migrate to postgresql