Included: functionality (copy/pasted from buildout-versions) to
actually record and print the picked versions. For this, two new
class-level attributes on the Installer are added.

TODO: testing whether the printing of what required what also
works.

The [versions] section is checked for a 'python' key.
Functionality copied from buildout-versions.
Includes documentation and tests.

Everything is in place now for actually implementing it.

I need to go through buildout-versions' finish() method, still.

    option_name=value

  as a short-hand for::

    buildout:option_name=value

Removed '-v' verbosity option from bin/test (just trying something)

Removing the verbosity might make it more obvious where the two failures occur that zc.recipe.testrunner insists exist when running on travis.

favor of the versions sections.

Add default versions to the versions section, if possible.
This means adding a versions section (if necessary/possible).

commit.

specific to the way I was developing on mac.

IncompatibleConstraintError.

       correctly.

``versions`` section), so you know longer need to include::

   versions = versions

in a ``buildout`` section when pinning versions.

       (which is how the buildout script gets generated).

Fix macro inheritance bug

       options were treated as errors.

       (This was an ill-considered temporary attempt to
       make used of the new bootstrap script easier.)

Moved the download locatiion to downloads.buildout.org.