Add "removed" mode

[dougwilson]

Sometimes a project may be so big, that even a deprecation cycle still might not be enough; after the next major that removes the feature it may be useful to have a "removed" message for some things that used to be deprecated.

I'm thinking perhaps add a remove property to deprecate:

var deprecate = require('depd')('my-module')
exports.missingfn = deprecate.remove.function('missingfn')

The function, property and other helpers would not wrap things, since they are meant for removed things (thus, what would you be wrapping?).

[dougwilson]

Unnecessary for now.