JulianDate.__eq__ crashes when not comparing to another JulianDate object

[alexamici]

Comparing a JulianData object to anything else than another JulianDate object crashes with:

AttributeError: <type> object has no attribute 'tt'

I would have expected to simply return False.

I didn't test it, but it seems to me that even comparing two JulianDate objects with an array of times would crash due to the fact that numpy.ndarray's do not have a defined truth value.

[alexamici]

I hit the problem on current release 0.6.1 and I just noticed that master contains some major refactoring, but bug is still present.

[brandon-rhodes]

Thanks for letting me know about the problem!

[brandon-rhodes]

I have just released Skyfield 0.8 with a fix for this issue. Thanks again for letting me know about it!