Runtime Mesh OBJ Importer and Exporter currently only supports triangle meshes.
This can be great help to anyone who wants to save changes they've made to their mesh within Unity, and get it back into Maya, 3ds Max or even Blender. Simple to use one line to encode your mesh and one more to export it, likewise one line to import your OBJ data and one more to load it into your Unity.
This project is open source on GitHub at https://github.com/octo-code/obj-unity3d