Require changes:

- no longer loads Mock and stub automatically, you must now
  require them explicitly:

    var Mock = require('minitest/mock')
    var stub = require('minitest/stub')

- using Mock.ExpectationError instead of Mock.MockExpectationError.
Requiring minitest no longer requires spec, mock nor stub.

You must now require them independently, using the minitest/spec,
minitest/mock and minitest/stub modules for Node.js or
requirejs/cajon.

You may also use the browser built minitest-spec.js,
minitest-mock.js and minitest-stub.js that must be loaded after
minitest.js is loaded.