Mixins execute backwards

In my application I do something like this

`mixins: [LoggedInMixin, UserIsBlaBla]`

The second mixin in the array depends on something in Meteor.user() so we need to make sure the user is logged in first. But, unexpectedly, mixins will run in reverse order so I have to reverse the array:

`mixins: [UserIsBlaBla, LoggedInMixin]`

No source file or test is named in the issue. Start by locating the mixin execution entry point in the repository and reproduce the example with two dependent mixins. Done means mixins run in the declared array order, with a regression test covering that order.

Written by the indexing model from the issue text.