Implement lesson tag filtering

[jrobind]

Links to #62

As part of the lesson tag filter feature, a user should be able to filter lessons by tag(s). It might make sense to create 2 tickets, one to handle the UI and the other to handle the filtering logic.

Things to consider:

• Where will the filtering controls live?
• Should the user be able to filter by multiple tags?
• Should we display something to the user in the event there are no matching lessons for the selected filter?
• Should the user be able to reset the filter state/selection?