Suggest event removals

[qchen59]

From ScheduleBot created by lyonva: lyonva#40

Note: When priority is a thing

• Your entire day is scheduled
• You have event 1 of priority 4
• You try to find time for another event of priority 3
  ScheduleBot should say there is no time, but can suggest replacing event 1 as it has less priority.

[Arcane94]

Must fix #46 before implementing this.