capybara-webkit has various development dependencies which can be a little
cumbersome to manage. With vagrant they can all be nicely bundled up in a VM and
installed automatically.
Several tests in driver_rendering_spec.rb require the identify command
that is part of Imagemagick. Without it they fail with output similar to
the following.
MiniMagick::Error:
Command ("identify -ping
/var/folders/y3/vfvjgwm91f1fmt2syh21czx40000gn/T/mini_magick20120115-49056-pwh5nl-0.png")
failed: {:output=>"sh: identify: command not found\n",
:status_code=>127}
