[WIP] Initial upgrade to decorators state 2

[josemarluedke]

This is an initial stab at upgrading to latest ember-decorators + babel 7.

This addon is breaking our app where another addon is using decorators state 2, probably because of the old dependency here of @ember-decorators/babel-transforms.

Also, I need to confirm that the changes related to @ember-decorators/argument are correct. Essentially the option defaultIfUndefined is not available anymore.

[josemarluedke]

I'm getting the following error from @ember-decorators/argument.

object.js:20 Uncaught TypeError: Cannot convert undefined or null to object
    at Function.getOwnPropertyDescriptor (<anonymous>)

Is anyone more familiar with this to help out?

[cyril-sf]

@josemarluedke Do you still get the same error if you rebase?

[josemarluedke]

I think this can be closed as State 2 decorators are not moving forward. We can keep using stage 1 decorators. See emberjs/rfcs#440.

[josemarluedke]

It would still be nice to have babel 7 and etc. But it make sense to be a new PR.