Mocks are no longer tied to the It scope.

When Mock is called from an It block, the mock's lifetime is tied to whatever the parent scope of the It block is (either Context or Describe).  The concept of an "It" scope still exists, but only for use in calls to Assert-MockCalled.
Merge pull request #176 from dlwyatt/RevertingItScope

Mocks are no longer tied to the It scope.
Update CHANGELOG.md