Make this library pip installable

[haixuanTao]

It seems that this library is the go to library for logging urdf. Could be neat to have it on pip to enable proper versioning. :)

[traversaro]

Indeed, this would be quite useful. A possible blocker is that the urdfdom-py dependency is missing on PyPI, but hopefully this can get sorted in ros/urdf_parser_py#85 .

As a related note (not sure if OT), even just having a 0.1.0 tag would be helpful, as we could at least package this in conda-forge (as there the urdfdom-py package is available: https://github.com/conda-forge/urdfdom-py-feedstock).