Updates to features, navigation, etc.

@BBonifield a few notes for you here:

There are a couple of new gems, one of which is dotenv-rails.  For running this app locally, a user should have a `.env` file with the required keys for certain things.  Here is a copy of my `.env` file locally: https://gist.github.com/createbang/76ae7f0433acd44201b9.  The only variables that I don't see on Heroku currently are the `KEEN_` values.  I just created an account for myself, but I imagine we'll want to have those filled in pre-deploy.

This commit is embarrassingly large, mostly because I was so caught up reacquainting myself with Rails that the work done started to get too expansive to break up, so I just put it in one commit.  This is uncharacteristic of my development style, just so you know.

I added a migration, and I can't remember if heroku's buildpack will automatically run any new migrations on deploy.  Just so you know a migration needs to occur.

I added a Heroku Scheduler task to the project, that will execute `bundle exec rake:accounts:project_leads:update_reminder_email` each day, but only send emails on Mondays.  I've never used Heroku Scheduler before, so it'd be good to get a second pair of eyes on this if you've had any experience getting it to work.

I think that's it!  Let me know if you want anything else adjusted or have any questions.  :boom: 

So this change will actually break the new user workflow.  The `_form` partial is being used to re-use the same form with a different URL (new vs. update) in both places.  So since the form tag is inside here now, the new user workflow will have two nested forms.