Switch from deprecated :public to :public_dir

Silences warnings in log of the form:

  :public is no longer used to avoid overloading Module#public, use
  :public_dir instead

Change-Id: I2810d961df3b9e7963e47d1787a793f07a69cfd3
Reviewed-on: https://gerrit.causes.com/24896
Reviewed-by: Greg Hurrell <greg@causes.com>
Tested-by: Greg Hurrell <greg@causes.com>
Use shotgun gem for tighter feedback loops in development

This gives us a means of reloading the app for every request, ensuring
any code edits are immediately reflected.

Change-Id: I810529b72dabf51666036283bd2c9427ca53e50a
Reviewed-on: https://gerrit.causes.com/24897
Reviewed-by: Greg Hurrell <greg@causes.com>
Tested-by: Greg Hurrell <greg@causes.com>
Sort `require` statements for tidiness

Change-Id: Ic391c5466c15cbf0ea3d875195ae1bafb5e44fb1
Reviewed-on: https://gerrit.causes.com/24898
Reviewed-by: Greg Hurrell <greg@causes.com>
Tested-by: Greg Hurrell <greg@causes.com>