Exploratory development for https://github.com/FriendsOfSymfony/FOSElasticaBundle/issues/410
Don't need postRemove.
Refactor to a single Listener class.  Update tests.
Re-add renamed Listener.
pre/postFlush configuration. Update documentation.
Remove upgrade doc.  Merk will add manually.
Remove debug.
Improve test coverage
Add test for ElasticaToModelTransformerCollection::hybridTransform
Remove unused method
removed duplicate methods
Better variable names
Merge pull request #432 from hardchor/duplicate-code-removal

Removed duplicate methods
Use constants of corresponding events classes rather than making assumption about string values.
Fixing reset command to allow resetting of just one type, starting to write test
Adding tests
Merge pull request #429 from craigmarvelley/improve-code-coverage

Improve test coverage
Merge pull request #433 from FriendsOfSymfony/fix-reset-command

Fix reset command
Fix tests
Adding support for enabling timestamps