Optimize Heroku Dyno Usage

[samithShetty]

The bot is currently running out of free monthly credits near the end of every month, resulting in the bot going offline for the last few days until the new month starts.

Currently, Heroku is the recommended way for users to self-host the bot for their own use. This is due to the fact that Heroku provides a decent amount of monthly free credits, and can provide the easiest non-technical setup (see #4 ) Having a lapse in bot uptime is definitely not acceptable, so the recurring processes in canvasCog.py need to be better optimized so that they don't eat up so many free credits.

In the meanwhile, this issue can be avoided by adding a credit card to the user's Heroku account which grants the account twice as many free monthly credits, but this is not a permanent solution.

[samithShetty]

Heroku shutting down free tier, will no longer be the recommended option for Canvas Bot. See #8 for more info