Allow read models to have non-string IDs.

There is no reason why a read model's id should be a string. Being able
to cast the ID to a string is enough.
Add tests for non-string read model id
Make the DBAL event store table name configurable.

There is now a bundle configuration option under
```
broadway:
    event_store:
        dbal:
            table: my_events
```
Defaults to `events`.

Fixes https://github.com/qandidate-labs/broadway/issues/90
Merge pull request #93 from lrqdo/db_event_store_config

Make the DBAL event store table name configurable.
Merge pull request #108 from mbadolato/in_memory_read_repo

In memory read repo