Using hardlinks to bring Editor and Plugins directories:

Both Unity3Sample and Unity4Sample use the same Editor and
Plugins directories.  Unity doesn't appear to work well with
symlinks.  Copying files around was too much to keep track of,
and a git submodule for both Plugins and Editor directories
seemed like overkill.

The following directories are now ignored:
Unity3Sample/Assets/Plugins
Unity3Sample/Assets/Editor
Unity4Sample/Assets/Plugins
Unity4Sample/Assets/Editor

A hardlink should be created between OKPlugins and:
Unity3Sample/Assets/Plugins
Unity4Sample/Assets/Plugins

A hardlink should be created between OKEditor and:
Unity3Sample/Assets/Editor
Unity4Sample/Assets/Editor