setup email service

[ahdinosaur]

some random guy made a nodemailer service for feathers: https://github.com/feathersjs/feathers-mailer.

• add new service to notifications topic, in the services folder
• hook service up into the main server top-level file
• install maildev as devDependency: https://github.com/djfarrelly/maildev
• add dev:mail script, move current dev script to dev:app, change dev script to be npm-run-all -p dev:*
• add necessary development mailer config for maildev: https://github.com/djfarrelly/maildev#configure-your-project