Use guaranteed binary and source compatibility between releases of Scalafmt

[joan38]

Fix for #252

[nedtwigg]

Looks like the change breaks older versions of scalafmt?

[joan38]

This drops the support for scalafmt < v0.7.0-RC1. Is it good enough? It's a pretty old version...

[joan38]

I tried to run the tests with gradle test but it doesn't seem to be the way to do and the CONTRIBUTING.md doesn't specify how to run the tests...

[nedtwigg]

Great! All it needs now is updated CHANGES.md:

• a summary of the change
• a link to the newly created PR

If your change only affects a build plugin, and not the lib, then you only need to update the CHANGES.md for that plugin.

If your change affects lib in an end-user-visible way (fixing a bug, updating a version) then you need to update CHANGES.md for both the lib and the build plugins. Users of a build plugin shouldn't have to refer to lib to see changes that affect them.

[nedtwigg]

bump