Added test to validate gutterball schema

This test will tell hibernate to validate the DB schema and
fail if there are any discrepancies b/w what liquibase created
and what hibernate expects.
Instead of having the empty test, how about this?  (This method will also save the cost of bringing up all the Guice stuff that we don't really need)

```java
public class DatabaseSchemaValidationTest {

    @SuppressWarnings("checkstyle:visibilitymodifier")
    @Rule
    public GutterballLiquibaseResource liquibase = new GutterballLiquibaseResource();

    @Test
    public void testSchema() throws Exception {
        // Setting the JPA module to validate the schema below. The fixture sets up the
        // Entity manager which will cause a failure if the schema is invalid.

       try {
            Properties overrides = new Properties();
            overrides.setProperty("hibernate.hbm2ddl.auto", "validate");
            Persistence.createEntityManagerFactory("testing", overrides);
        }
        catch (PersistenceException e) {
            fail("Schema did not validate");
        }
    }
}
```