[python] Added support for Python packages.
[ruby] Added support for Ruby packages.
[python] Improved Python packages support.

This now uses a requirements file to specify the packages to install.
[ruby] Improved Ruby packages support.
[packages] Removed failing Homebrew packages.
[packages] Removed unused Homebrew packages.
[install] Made install more portable.

This was failing with a certain shells.
[ruby] Added source for Ruby packages.

This is required but was not found originally since all packages were
already installed.
[mercurial] Removed unnecessary extensions.
[packages] Added additional (disabled) packages.

The boost-build package does not build, so these are currently disabled.

- boost-build
- boost-bcp
[emacs] Added a few more themes.
[install] Fixed some warnings.
[packages] Improved definition of Homebrew taps.
[packages] Added python and nginx taps for Homebrew.
[emacs] Use local rtags instead of installed.
[package] Fixed a bug in Homebrew installs.
[emacs] Removed comsim-mode.

This hasn't been used or worked in many years.
[emacs] Conditionally require packages.

This uses (when (require ...)) instead of commenting out lines to allow
for packages that are not installed.
[emacs] Moved packages requiring emacs-24.

Several packages that actually require emacs-24 were in the wrong
section.
[packages] Added Perforce Jam to packages to install.