module_source won't let you specify providers

[edulop91]

Fogg's module_source feature doesn't let you specify providers such as:

module foobar {
    source = ""asfdasdfaf"

    providers {
        aws = aws
        aws.us-east-1 = aws.us-east-1
    }
}

[mbarrien]

While we're here, may also want to future proof for other cases we want to add things to a module, such as Terraformm 0.13's depends_on, or possibly for_each/count