Feature/13 reminder email bugs

#### What's this PR do?
* Addresses a couple bugs with the new email reminder logic.
* Adds functionality to catch outbound emails in development mode and preview them in the browser, making local testing easier
* Adds functionality to force sending the email reminders (i.e. does not have to be Monday), making local testing easier

#### Where should the reviewer start?
The diff is pretty small, so it doesn't need a lot of additional explanation.

#### How should this be manually tested?
Create a user with two active projects and one inactive project.  Previously, that user would have received two emails, and both of them would include all three projects.  Now, the user receives a single email that only contains the active projects.

#### Any background context you want to provide?
N/A

#### What are the relevant tickets?
https://sprint.ly/product/21477/item/13
The point of `force_send` is so you can do `rake task[true]` to force it even though it's not Monday.  Previously, you'd need to comment out the line in order to test locally.