Rename glider module to slocum

The 'glider' module needs to be renamed back to slocum..this is to make this world more robust as we start doing things with the oceangliders. 

If oceanscouts go into the same buckets (and they probably should), this may necessitate the `get_path_glider` moving to another module. Or, maybe the oceanscout module could import and use it a la R's 'reexport'?