#8 - Add MongoDB text search example.

The sample reads the Spring IO blog Atom feed and performs text search on it.

We use manual index creation and query via MongoTemplate as well as automatic index creation and derived queries via repositories.

Original pull request: #10.
#8 - Some polishing of the example.

Introduced the usage of Lombok to be able to get rid off the getters and setters. Simplified the configuration to use Spring Boot's auto-configuration. The initializer is now an enum manually triggered with a MongoOperations instance. Switched from MongoTemplate to MongoOperations where possible. Polished some JavaDoc.

Original pull request: #10.