This is a copy of the ceedling vendor directory that can be created by the ceedling gem. You can easily install this gem using the following command.

gem install ceedling

As described on the ceedling gem page you can...

...deploy all of ceedling's guts into a folder. This allows it to be used without having to worry about external dependencies.

ceedling new [your new project name]

This SpinDance/ceedling repository is a copy of those "guts" copied from the [your new project name]/vendor/ceedling directory. It is here only for convenience and the content has not been modified from that which is created by the 0.13.0 version of the gem.