Revert "Remove Impression modeling"
Revert "Remove Impression modeling"

This reverts commit 9e1bef5977309bf00dbbce10716698f654396962.

pombredanne/readthedocs.org,rtfd/readthedocs.org,safwanrahman/readthedocs.org,davidfischer/readthedocs.org,rtfd/readthedocs.org,safwanrahman/readthedocs.org,rtfd/readthedocs.org,safwanrahman/readthedocs.org,tddv/readthedocs.org,pombredanne/readthedocs.org,rtfd/readthedocs.org,davidfischer/readthedocs.org,pombredanne/readthedocs.org,davidfischer/readthedocs.org,tddv/readthedocs.org,safwanrahman/readthedocs.org,tddv/readthedocs.org,davidfischer/readthedocs.org