Do not find_package(yaml-cpp)

While it appears that https://github.com/baxelrod/dynamixel_pro_controller/commit/94d6859f55bd8061676c13ad55a220e027bd9dc2 fixed the compilation problems in the buildfarm with yaml-cpp, adding the dep in the `package.xml` is the portion that actually fixed the problem. In actuality, the `find_package(yaml-cpp)` is failing on all current releases of Ubuntu and Fedora, as there is no `Findyaml-cpp.cmake` packaged with the system's yaml-cpp. The reason that this is not a fatal error is that you are currently hard-coding the library name and not using what WOULD be set from the `find_package`.

It would suffice to simply remove the `find_package(yaml-cpp)` from `CMakeLists.txt`, but it would likely be better to also start using the pkgconfig's value (from https://github.com/baxelrod/dynamixel_pro_controller/pull/2) at https://github.com/baxelrod/dynamixel_pro_controller/blob/master/CMakeLists.txt#L83 instead of hard-coding the library name.

If the other PR gets merged, I can generate another PR that does this, if you like.

On another note, I don't believe that `rosdep.yaml` files are used any more in light of the rosdep database in rosdistro.

Thanks,

--scott