Update to work with setuptools 34

Editing while reading

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Do not remove an existing egg.

After a dist is fetched and put into its final place, compile its
python files.  No longer wait with compiling until all dists are in
place.

This avoids calling redo_pyc at the same time by two parallel buildouts.
It might not be so bad, but it seems better (and faster) to avoid it.

See discussion at https://github.com/buildout/buildout/issues/307

When installing an egg to a location that already exists, keep the
current location (directory or file).

This can only happen when the location at first did not exist and this
changed during the buildout run.  We used to remove the previous
location, but this could cause problems when running two buildouts at
the same time, when they try to install the same new egg.

Fixes #307.

In the tests, filter out an invisible control character.

This avoids invisible control characters popping up in some terminals, like `xterm`.

Note that this may affect tests by buildout recipes.

Fixed bootstrap test for newer setuptools.

setuptools used to say this:

    No local packages or download links found for zc.buildout==UNKNOWN

Since setuptools 25.1.0 it says this:

    No local packages or working download links found for zc.buildout==UNKNOWN

See also https://github.com/pypa/setuptools/pull/609/files

Fix typo

No python 3.3 and newer versions of the other pythons

Remove Python 2.6 and Python 3.2 support

Refs #297

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Simple Fix for 'Extending sections (macros)' in combination with += and -=.

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It was originally called 'path'

Turn proposed patch into a pull request.

https://github.com/buildout/buildout/issues/257#issuecomment-159423299

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Nicer version constraint logging + better requirement conflict info logging

The tests fail to run due to the deprecation warnings, so I stripped 3.2 out of travis.

Added 3.5 instead as that's the most modern version.