astropy for converting Altitude/Azimuth into Equatorial and back

[peterjc]

This is now in astropy v1.0, see eteq/astropysics#21 and example http://docs.astropy.org/en/v1.0.1/coordinates/observing-example.html

This should allow replacement of alt_az_to_equatorial and equatorial_to_alt_az in telescope_server.py