Revert "Merge pull request #130 from jhoblitt/has_element"

This reverts commit f7a18189ec338b01b0fc89d75def832753af3868, reversing
changes made to 36a7b29630a4d4de17af79b5dd4e9491ec20b123.

I'm reverting this change because of concerns raised by Peter Meier that
it duplicates the "in" operator in the DSL.  The "in" operator is new
information that I did not posses when I made the decision to merge.
Because of this new information I'm un-merging and continuing the
discussion in the comments of
https://projects.puppetlabs.com/issues/19272

Reference: GH-130