Add new command - mars weather

[mikelax]

As a user, I would like to be able to know the current weather on Mars.
The slash command params would be: /spacebot mars weather

A nice to have feature would be to have the weather report calculated automatically each day by a scheduled lambda function. The output of this function would be a "weather report" image that could then be served in response to above command.

We could look at the past data for ~1484 Sols and calculate some stats like high/low, etc so image could show current values on scale instead of just displaying raw numbers without any real context.

Sources:
https://cab.inta-csic.es/rems/
https://cab.inta-csic.es/rems/wp-content/plugins/marsweather-widget/api.php
http://cab.inta-csic.es/rems/rems_weather.xml
https://weather.com/science/news/check-weather-mars-where-nasas-maven-headed-20131119