Remove include Enumerable from ActiveLdap::Base

Since e7f6ab87dccd427d24f7430c826fca15734533ad there has been no ``#each`` method to power Enumerable and so it's now a redundant include.
Merge pull request #104 from unboxed/no-more-enumerable

Remove include Enumerable from ActiveLdap::Base

Patch by Murray Steele. Thanks!!!