Updates the legalese.
Updates DestroyedAt for Rails 4.1

Removes `.with_default_scope` which has been deprecated.

Removes `m` as a development dependency, since it is not `minitest 5`
compatible.

Bumps major version.

Closes #36
Merge pull request #37 from dockyard/md-36-rails_4_1

Updates for Rails 4.1