Fix typo in config sample about overrides
Fix typo in config sample about overrides

Missing "overrides" key. Fixes gh-323.

royclarkson/spring-cloud-config,royclarkson/spring-cloud-config,marbon87/spring-cloud-config,royclarkson/spring-cloud-config,marbon87/spring-cloud-config,marbon87/spring-cloud-config,fkissel/spring-cloud-config,spring-cloud/spring-cloud-config,shakuzen/spring-cloud-config,fkissel/spring-cloud-config,fkissel/spring-cloud-config,spring-cloud/spring-cloud-config,spring-cloud/spring-cloud-config,shakuzen/spring-cloud-config,shakuzen/spring-cloud-config