Upgraded BatchBundle to dev branch
Added upgrade documentation
Fixed spec
Merge branch 'master' into task/batch_bundle_0.2

Conflicts:
	CHANGELOG.md
	composer.json
Switched to stable version of batch bundle
Merge branch 'master' into task/batch_bundle_0.2
Merge pull request #1210 from akeneo/task/batch_bundle_0.2

batch bundle 0.2 upgrade