* Introduced abstraction for getting migrations
This would allow a webpack migration source which is compatible with bundling.
* Fixed migration validation with custom migration source
* Fixed issues after rebasing on muti directory PR
* Renamed parameter and fixed error message
* Addressed some PR comments
* Finished comment
* Moved filename extension filtering into fs-migrator
* Added test showing in memory custom migration source
* Cleaned up how to get config
* Fixed failing test
* Hopefully fix tests
* Fix Node.js 10 support in tests
