Add password reset/change functionality

[walter]

This implements the ability for users to request a password reset and receive an email with a token to change their password.

It also allows for logged in users to change their password by directly navigating to /password/edit.

Currently WIP. Waiting for PR #32 to update dependencies before adding necessary addition of Bamboo dependency to mix.exs.

May need additional styling, too.

Demonstrates functionality needed to satisfy #36.

Appreciate feedback on if there are any security gotchas with issuing a Phoenix.Token for Authorization id.