Added basic mailer for invoices. Added dev configuration for mailer.
Added a route for the mailer and 'deliver' action to the invoice_controller.
Adding local_env config file to ignore list (to store sensitive params/vars).
Merge branch 'add-mailers' into development

* add-mailers:
  Added a route for the mailer and 'deliver' action to the invoice_controller.
  Added basic mailer for invoices. Added dev configuration for mailer.
Added import of local_env config file.
Updated README.
Invoices: updated mailer to attach a generated pdf version of the invoice. Now the user is redirected after emailing (or attempting). Updated mailer to temporarily redirect all mail to testing address.
Added 'email invoice as pdf' link to invoice 'show' view.
Added confirmation dialog to the 'email invoice pdf' link