Moved from capistrano to mina

- Moved to mina which is much faster and simpler
- Also, enforced permissions for adding a mindlog to channel
Fixed security bug in updates controller

- Added access rules for updates
- Fixes #38
Fixed post-sign-in redirects

- Fixes #3
- Adds additional ability to redirect to previous page even if there
was no error.
- Improved documentation and indentation in application_controller.rb