Directly output barotropic velocities
Directly output barotropic velocities

Because these arrays have a different shape to all the others - they only cover the computational domain, not the halo - te write_output subroutine wasn't correclty outputting the data.
Directly saving the arrays rather than using the subroutine fixes this issue. This closes #130.

edoddridge/MIM,edoddridge/aronnax