Should fix https://travis-ci.org/buildout/buildout/jobs/39918144

Closes #203

Some background: PEP 453 introduced the 'ensurepip' module to Python 3.4.
'make install' runs 'python3.4 -m ensurepip' which installs setuptools
into site-packages.  Our test suite doesn't like that.  Luckily,
Python's ./configure has an option to disable ensurepip.

Travis thinks something is wrong when the script produces no output in
10 minutes, which leads to sporadic test failures like
https://travis-ci.org/buildout/buildout/jobs/39916822

If PYTHON_VER is not known to the Makefile, don't fall back to
PYTHON_MINOR of 2.7.3, instead ask the user to specify a correct
PYTHON_MINOR explicitly.  Otherwise you get weird failures like #203.

Also allow the user to override PYTHON_MINOR on the `make` command line,
e.g.

    make PYTHON_VER=3.3 PYTHON_MINOR=3.3.6

Closes #202.

Fix for buildout 2.2.3 upgrade/downgrade problems

non-matching versions.

Ignoring version conflicts for buildout and setuptools, this enables
buildout/setuptools upgrades/downgrades after a bootstrap.

Whatever the method we used to find it, cache the result. Not just in one of
the cases. And it makes the method more readable as it doesn't mix functionality

Often it is unclear why buildout takes a long time on something, this logger
statement might make it much clearer

This way it is more clear that we're trying several things one after the
other. And it is nicer to read this way.

- Performance enhancment via https://github.com/buildout/buildout/pull/194
- Fix manifest

193 performance

Introduce improved easy_install.py Install.install function. Originally commited in 98b7c55cb8b8e39e4835b5dd4223fda55f519890

Fix for #184

See #184, a comma doesn't work (like it *does* inside a logger call) inside an exception.

Close various files when finished writing to them; fixes ResourceWarnings and some PyPy uses.

Unify three checks for a file being changed into one function. Note that python < 3.3 raise IOError if a file is not found, while python >= 3.3 raise FileNotFound, a kind of OSError. EnvironmentError is a common superclass on all versions and in fact is where `errno` is defined.

Close various files when finished writing to them. This avoids ResourceWarnings on Python 3, and better supports doctests under PyPy.

Fix Python tarball download in Makefile by following HTTP redirects

List Python 2 and 3 support in setup.py