Cleaned up the implementation to make greater use of and duplicate
less code from zc.buildout.easy_install.

Added ability to supply entry points directly. This is useful for
packages that don't declare their entry points.

No longer generate "py-" scripts implicitly.  Added a new option,
interpreter, to request such scripts and specifu their names.

No longer generate "py-" scripts implicitly.  We no longer create one
for zc.buildout when bootstrapping.

Added an error-reporting API for use by recipes.

Added a help command-line option.

Fixed a bug in the way that recipe eggs were loaded.

Added an environment variable hack to cause the buildout to use a
local empty index when running tests. This allows most of the tests to
be run when offline and doesn't slam pypi at other times.

zope.testing.

Added an option to supply entry points directly. This is useful for
packages that don't declare their entry points.

No longer generate "py-" scripts implicitly.  Added a new option,
interpreter, to request such scripts and specifu their names.

Increased default buildout logging.

invoking easy install.  This should make things go faster in practice.

Stop giving setuptools special treatment when downloading.
Unfortunately, this means tests take a lot longer to run and probably
that they can only be run when connected. :(
Maybe I should figure out a way to get stuptools to use a different
default index when running tests. :/

It would have broken old bootstrap scripts.  Now my problem is that if
I update buildout in a way that recipes depend on, people will have to
update their buildouts by running the bootstrap script. This isn't ideal.

generated script paths.

Added an arguments option to specify source for arguments to be passed
to entry points.

generated script paths.

The sample buildout is now created using the bootstrapping mechanism
and so has a normal layout.

No longer read ~/.buildout/.default.cfg, when running tests.
(We do read a ~/.buildout/.default.cfg when testing that function, but
we manipulate HOME so that we control what is read.)

The characters "-", "." and " ", weren't allowed in section or
option names.

Substitutions with invalid names were ignored, which caused
missleading failures downstream.

- Now require a recipe option (and therefore a section) for every part.