Add basic mood stats

- new ‘moods’ command, default number of days is 7, unless user passes
in their own time period. i.e. ‘moods 14’ should return a mood summary
containing average mood level for past 14 days, along with 3 most
recent mood entries
Add default value for num_days in case of empty input

- Messy…maintaining a default number of days in two different classes,
potential for data inconsistencies
Add context specific quotes for certain mood entries

- Low moods get inspirational quotes
- High moods get calming quotes
- Added a Quote model
Update summary string for mood entry

Don’t really need the summary if a quote is getting sent. The quote
serves as the implicit reminder that the checkin was received.
Update notes