[collada_urdf_jsk_patch][README.md] update readme

jsk_ros_patch/collada_urdf_jsk_patch/README.md

@@ -1,7 +1,21 @@
 collada_urdf_jsk_patch
 ======================
-collada_urdf_jsk_patch is a patched version of collada_urdf to use with assimp *3.1*.
-hydro and ubuntu 12.04 provides assimp *2.0* and it has critical bag.
 
-collada_urdf originally uses assimp but collada_urdf_jsk_patch uses assimp_devel.
-assimp_devel provides assimp *3.1.1*.
+This is a yet another version of [collada_urdf](http://wiki.ros.org/collada_urdf) package.
+
+Original `collada_urdf` depends on `libassimp` package provided by Ubuntu Update and has a serious bug on visual when spawning exported URDF file into Gazebo.
+
+This patched version solved this problem using newer `assimp` library (>= `3.1`).
+
+## For Developers
+
+This package depends on `assimp_devel` which provides newer version of `libassimp` (`3.1.1`).
+
+Current ubuntu distributions using assimp older than `3.1` must use this package instead of original `collada_urdf` and `libassimp`.
+
+
+- Ubuntu 12.04 LTS: `2.0.863+dfsg-2` (< 3.1)
+- Ubuntu 14.04 LTS: `3.0~dfsg-2` (< 3.1)
+- Ubuntu 16.04 LTS: `3.2~dfsg-3` (>= 3.1)
+
+We will be able to disable this package and `assimp_devel` on kinetic (because kinetic supports 16.04 or newer).