[TIP] tox-1.6: support for install_command, develop, py25

[holger krekel]

tox-1.6: support for install_command, develop, py25
=============================================================

Welcome to a new release of tox, the virtualenv-based test
automation manager.  This release brings some new major features:

- installer_command: you can customize the command user
  for installing packages and dependencies. Thanks
  Carl Meyer.

- usedevelop: you can use "develop" mode ("pip install -e")
  either by configuring it in your tox.ini or through
  the new "--develop" option. Thank Monty Tailor.

- python2.5: tox ships internally virtualenv-1.9.1 and can
  thus run tests create virtualenvs and run tests against 
  python2.5 even if you have a newer virtualenv version 
  installed.

While tox-1.6 should otherwise be compatible to tox-1.5, 
the new $HOME-isolation ($HOME is set to a temporary directory
when installing packages) might trigger problems if your
tests relied on $HOME configuration files -- which they 
shouldn't if you want to repeatability.  If that
causes problems, please file an issue.

Docs and more information at:

    http://testrun.org/tox/latest/

have fun,
holger krekel

1.6 Changelog
--------------

- fix issue35: add new EXPERIMENTAL "install_command" testenv-option to
  configure the installation command with options for dep/pkg install.
  Thanks Carl Meyer for the PR and docs.

- fix issue91: python2.5 support by vendoring the virtualenv-1.9.1 
  script and forcing pip<1.4. Also the default [py25] environment 
  modifies the default installer_command (new config option)
  to use pip without the "--pre" option which was introduced 
  with pip-1.4 and is now required if you want to install non-stable 
  releases.  (tox defaults to install with "--pre" everywhere).

- during installation of dependencies HOME is now set to a pseudo
  location ({envtmpdir}/pseudo-home).  If an index url was specified
  a .pydistutils.cfg file will be written with an index_url setting
  so that packages defining ``setup_requires`` dependencies will not
  silently use your HOME-directory settings or https://pypi.python.org.

- fix issue1: empty setup files are properly detected, thanks Anthon van
  der Neuth

- remove toxbootstrap.py for now because it is broken.

- fix issue109 and fix issue111: multiple "-e" options are now combined
  (previously the last one would win). Thanks Anthon van der Neut.

- add --result-json option to write out detailed per-venv information
  into a json report file to be used by upstream tools.

- add new config options ``usedevelop`` and ``skipsdist`` as well as a
  command line option ``--develop`` to install the package-under-test in develop mode.
  thanks Monty Tailor for the PR.

- always unset PYTHONDONTWRITEBYTE because newer setuptools doesn't like it

- if a HOMEDIR cannot be determined, use the toxinidir.

- refactor interpreter information detection to live in new
  tox/interpreters.py file, tests in tests/test_interpreters.py.