Next major version

[DivineOmega]

This PR makes breaking changes that will require a new major version release. It includes the following changes.

• PHP 7.1 minimum
• Source field validation via Omega Validator
• Enforce method argument and return types in the source and destination interfaces
• Newer version of PHP Unit

To do:

• [x] Document source data validation
• [x] Move Eloquent source/destination to separate package (repo)
• [x] Move Doctrine source/destination to separate package (repo)
• [x] Move PDF destination to separate package (repo)

[DivineOmega]

@peter279k Thanks for the code review. Most of these are now resolved.

On the remaining unresolved points, you mention type hints, but do you mean return types?

[DivineOmega]

The Eloquent, Doctrine and PDF sources/destinations have now been moved to their own repos.

• https://github.com/DivineOmega/uxdm-eloquent
• https://github.com/DivineOmega/uxdm-doctrine
• https://github.com/DivineOmega/uxdm-pdf-destination

[DivineOmega]

Source data validation has also been documented.

• https://github.com/DivineOmega/uxdm/pull/25/files#diff-04c6e90faac2675aa89e2176d2eec7d8R100