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
Reverted the introducion of BC classes for beberlei\assert
Added original message to assertion
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