Break hard dependency on Paste.

Working toward Py3k support.

Fork 'paste.exceptions.middleware.Supplement' and support code.

Make import of 'paste.httpexceptions' conditional.
Remove SyntaxError under Py3k.
Be explicit about bytes in app_iter.
Py3k compat.
Indirection around time.time to deal with Py3k difference.
Suppress nanny deprecations under Py3k.
Suppress deprecation warning under Py3k.
Suppress resource warnings under Py3k.
Ignore derived.
Add support for Python 3.2 / 3.3.
Add 'setup.py docs' alias.

Installs Sphinx.
Add support for building docs / testing snippets under 'tox'.