The deprecation of `scope` prop should be addressed in guide

[Justineo]

Since 2.5.0 we just replaced all scope with slot-scope in the guide, which may cause confusion among users. We should clearly address that scope is deprecated and slot-scope should be used instead.

[bison1994]

so efficiently. thanks

[BalGuldur]

Pls, write in documents info for users who don't update to 2.5.0 version. Becourse it's confusion users with Vue < 2.5, when they try implement slot-scope.
Like "for Vue version < 2.5.0, use scope".
Thx.

[Justineo]

/ping @chrisvfritz

[chrisvfritz]

I agree. I'll try to get to this when I can, but a PR is welcome in the meantime.