Use setup tools instead of distutils for the setup.py script
This is the new recommended way to distribute packages, see:
https://python-packaging-user-guide.readthedocs.org/en/latest/current.html

Remove the pkg-info file, this file is created by setup tools when building the project.
Some infos are not correctly exported to the PKG-Info file (the metadata version is still 1.1).
This is a known bug: https://bitbucket.org/pypa/setuptools/issue/219/emit-metadata-12-data

Cherrypicked from develop branch to hotfix v1.6.2 branch
Fix install_requires syntax, allow python 2.6
install_requires tries to install python on python > 3.3

Remove this line as we don't want to install python.
I thought it would only check if it's the right version, in fact it tries to install Python ... (build failing on Travis)
Change rights of declarations_cache.py and templates_tester.py
from -rwxr-xr-x+ to -rw-r--r--+, so that all the files have the same
execution rights.
Bump version number to v1.6.2
Update the doc for v1.6.2
Merge branch 'hotfix/v1.6.2'