Release v1.7.0

* Accept `:depth` option for Recursive membership validator strategy instance [#73](https://github.com/github/github-ldap/pull/73)
* Deprecate `depth` argument to `Recursive` membership validator `perform` method
* Bump net-ldap dependency to 0.10.0 at minimum [#72](https://github.com/github/github-ldap/pull/72)