Catch and Handle 500 error from NASA API

[mikelax]

As a user, I don't want to see an internal error message when running an apod command, but rather a friendly message of what happened.

example command: /spacebot apod 2009-10-17
This API is returning a 500 error from NASA, this should be caught and return a message to the user that there is a problem returning the image for this specific date, please try a different date.

We should catch errors from NASA for all APIs, not just apod.

[jantznick]

Is there still a need for this? Would be happy to help out!

[mikelax]

@jantznick yeah if you want to take a shot at this, that would be great.
I would think that if the request was for a random image, then we could just generate a new date automatically without needing to alert the user.