No robot model when using display.launch (again)

[gavanderhoorn]

Similar to #4. Seems the commits merged in PR #5 did not take the install location specified in the CMakeLists.txt into account.

AFAIU the current layout of the package will make it work either in the source / devel workspace, or the install workspace (due to present / missing urdf_tutorial/ subdir). I can change the launch files or the CMakeLists.txt, but don't know what the preferred situation is.

[isucan]

We should use a layout for the launch files that is the same in the install and the devel locations, so things work in both cases. It sounds like to me we may need to move files around and update the CMakeLists.txt as well?