fix zsh tab completion for symlinks (#169)
fix zsh tab completion for symlinks (#169)

- add '-L' flag to 'find' command used, for example, for tab completion of launch files and package nodes/executables
- building a workspace with catkin tools creates symlinks in a package's libexec folder, in which case the tab completion for the executable with rosrun didn't work
ros/ros,ros/ros,ros/ros