https://github.com/jsk-ros-pkg/jsk_common/pull/387 was wrong, we should not SKIP_PKG_CONFIG
Merge pull request #394 from k-okada/assimp_devel

https://github.com/jsk-ros-pkg/jsk_common/pull/387 was wrong.
Merge branch 'master' of http://github.com/jsk-ros-pkg/jsk_common into assimp_collada_urdf