We now allow registering CustomConversions to register custom converters (read and write targets). CustomConversions registers by default JSR-310, Joda Time and ThreeTen backport type converters.
These types (LocalDate, LocalDateTime) can be used in domain classes and with query method arguments. Date-only types map to Cassandra's date type, Date and time types map to Cassandra's timestamp type. Type mapping works for singular and collection types (List and Set).
```
@Table
public Person
@Id String id;
java.time.LocalDate date;
@CassandraType(type = Name.TIMESTAMP)
java.time.LocalDate timestamp;
List<org.threeten.bp.Instant> timestamps;
}
```
Original pull request: #68.
