Support ember 3.10, drops support for decorators

[GavinJoyce]

extracted from GavinJoyce#1
fixes #640 and resolves some of the issues described in #635

This PR is a breaking change as it drops support for decorators which have proven somewhat unstable. They were introduced a year ago in #583 so they are likely used by some apps. A good path forward would be to create ember-cp-validations-decorators which can depend on this addon and provide decorators support.

[GavinJoyce]

This is passing on all scenarios except for beta and canary:

I've opened an issue to track that: #642

[GavinJoyce]

We're running this in production for @intercom at the moment

[cah-danmonroe]

GavinJoyce/ember-cp-validations.git#8ba9fec36a2b3269bb95b66b0a2c68a832d6921d Fixes over 70 errors we had going from 3.9 to 3.10. Please merge

[offirgolan]

@GavinJoyce thanks for taking the time to resolve all of the current issues! Once this PR gets merged, I'll release a new beta version.

If the decorator support has been causing so many issues, I say we remove it altogether and I'll make a note of it in the new beta version's changelog. Feel free to remove it completely if thats necessary to get this working in 3.10+.

[GavinJoyce]

@offirgolan I've removed the remaining references to decorators, this should be good to go now

[offirgolan]

Thanks @GavinJoyce! Released under v4.0.0-beta.9.

[Alonski]

Awesome work @GavinJoyce !!!

[jderr-mx]

Awesome work, thank you!

[alejandrodevs]

Awesome. Thank you all!

[BryanCrotaz]

I'm seeing this bug with beta 9 and ember 3.10.2

Edit: IGNORE - npm had pulled in two versions of this addon