Add pending deprecation warnings for Python 2.7 and 3.4
Add pending deprecation warnings for Python 2.7 and 3.4

This change adds pending deprecation warnings for both Python 2.7
and 3.4. Both of these Python versions have reached end-of-life
and no longer receive security updates. Future versions of PyKMIP
will drop support for both of these Python versions.

OpenKMIP/PyKMIP,OpenKMIP/PyKMIP