This reverts commit 029ed106.

six is necessary for making these scripts cross compatible
between python 2.x and 3.x

Changes:
Add six to python_deps.include
Include python_deps.include to all Dockerfile templates in test directory
Include python_deps.include to all Dockerfile templates in stress_test directory
Include python_deps.include to all Dockerfile templates in interop_test directory
Replace print statements with print function calls (from futute..)
Replace .iteritems() with .items() wherever necessary
use six.moves to import BaseHTTPServer
Generate new dockerfiles using generate_projects.sh

Add dockerfile template for python_pyenv_x64 docker image
Generate the dockerfile using generate_projects.sh
Modify run_tests.py to include python3.5 and python3.6
Runs python_jessie_x64 for python versions 2.7 and 3.4, and
python_pyenv_x64 for python versions 3.5 and 3.6