The bounty-list partial now shows a message instead of displaying nothing if the passed bounty list is empty.
Don't show sections of the Artist#show page that are empty.
The development and test environments now use a generic secret token.

Use the dotenv gem in production to set the secret token via the
SECRET_TOKEN environment variable.
Fix a typo in the secret token file.
Fix a typo in the secret token file.
Update gems to latest versions.
Rake now adds an extra newline at the end when generating the structure.sql file.
Add a custom matcher to simplify checking if a completed bounty is displayed.
Move custom RSpec matchers to spec/support/matchers, which is the conventional place to put custom matchers.
Redesign the adult-only filter. Now the default level doesn't hide bounties the viewer is associated with (by ownership or by accepting the bounty).
Add tests for the Artist#show page's bounty displays.