Indexing orbit with integration time fails

[jamesmlane]

Orbit instances should be able to be indexed by times after integration, as long as the time is within the integration range. This fails for non-array arguments. The error is of slightly different origin depending on whether astropy units are used.

Example for astropy units

from galpy import potential, orbit
import numpy as np
from astropy import units as apu

pot = potential.MWPotential2014
o = orbit.Orbit()
times = np.array([0,1,2])*apu.Gyr

o.integrate(times,pot)
o(times[-1])

Throws an error on line 4236 when calling len(t).

Example for no astropy units

from galpy import potential, orbit
import numpy as np

pot = potential.MWPotential2014
o = orbit.Orbit()
times = np.array([0,1,2])

o.integrate(times,pot)
o(times[-1])

Throws an error on line 4261 because isinstance(t,(int,float)) returns False for numpy dtypes, then len(t) is evaluated.

[jamesmlane]

I think this can be fixed by just calling t= np.atleast_1d(out[0]) right away after the first if/elif/else statement in _call_internal to make it an array, and then refactoring the remaining conditional statements