Add formula for Distribute for Python.

"Distribute" is a "setuptools" replacement for Python, and is
a prequisite for "pip". Homebrew suggests using pip to install
Python modules required by a few brews.

This brew, by design, will only install against a Homebrew-built
version of Python, with instructions for installing
distribute against a custom Python.

Formula/distribute.rb

@@ -0,0 +1,45 @@
+require 'formula'
+
+class Distribute <Formula
+  url 'http://pypi.python.org/packages/source/d/distribute/distribute-0.6.13.tar.gz'
+  homepage 'http://pypi.python.org/pypi/distribute/0.6.13'
+  md5 '43460b429e86bf0da2bb18574d63ec0c'
+
+  def caveats
+    <<-EOS.undent
+      This formula is only meant to be used against a Homebrew-built Python.
+      It will install itself directly into Python's location in the Cellar.
+    EOS
+  end
+
+  def install
+    python = Formula.factory("python")
+    unless python.installed?
+      onoe "The Distribute brew is only meant to be used against a Homebrew-built Python."
+      puts <<-EOS
+        Homebrew's "distribute" formula is only meant to be installed against a Homebrew-
+        built version of Python, but we couldn't find such a version.
+
+        The system-provided Python comes with "easy_install" already installed, with the
+        caveat that some Python packages don't install cleanly against Apple's customized
+        versions of Python.
+
+        To install distribute against a custom Python, download distribute from:
+          http://pypi.python.org/pypi/distribute
+        unzip, and run:
+          /path/to/custom/python setup.py install
+      EOS
+      exit 99
+    end
+
+    system "#{python.bin}/python", "setup.py", "install",
+              "--install-scripts", bin,
+              "--install-purelib", python.site_packages,
+              "--install-platlib", python.site_packages
+
+    (prefix+"README.homebrew").write <<-EOF
+distribute's libraries were installed directly into:
+  #{python.site_packages}
+EOF
+  end
+end