Add a command to drop the dbal event store schema.

This is useful when automating end-to-end tests.
Import `\Exception` in the Bundle commands.
configured and ran php-cs-fixer
Update beberlei/assert to ~2.0

- Added the recommended compatibility classes under Broadway\Assert
- Updated usages of Assert\Assertion to Broadway\Assert\Assertion
Proposal for a CHANGELOG
Fix test after release Symfony 2.6: fixes #97
Merge pull request #98 from wjzijderveld/fix_test_after_symfony_26

Fix test after release Symfony 2.6: fixes #97
Composer timeout: disable GC
Added reference to IRC in README
Merge pull request #100 from wjzijderveld/add_irc_channel_to_readme

Added reference to IRC in README
Merge pull request #99 from wjzijderveld/composer_garbage_collection

Composer timeout: disable GC
Reverted the introducion of BC classes for beberlei\assert
Added original message to assertion
Merge pull request #79 from lrqdo/drop_event_store_command

Add a command to drop the dbal event store schema.
Merge pull request #84 from othillo/php-cs-fixer

configured and ran php-cs-fixer
Updated branch alias to 0.4.x
Merge pull request #88 from wjzijderveld/changelog

Proposal for a CHANGELOG
Merge pull request #106 from wjzijderveld/update-branch-alias

Updated branch alias to 0.4.x
Merge pull request #85 from DRvanR/master

Update beberlei/assert to ~2.0
Make the DBAL event store table name configurable.

There is now a bundle configuration option under
```
broadway:
    event_sourcing:
        dbal_event_store:
            table_name: my_events
```
Defaults to `events`.

Fixes https://github.com/qandidate-labs/broadway/issues/90