Fix for issue uploading Logos

[briri]

Fixes #620.

Changes proposed in this PR:

• We installed the lighter weight GraphicsMagick on the servers
• Add binstubs for the ImageMagick convert and identify commands
• Update Dragonfly config to tell it to use the binstubs

We will need to schedule time with @ashleygould to get GraphicsMagick installed on the prod hosts

To test:

• If logging in as an organizational admin
  • Go to the Admin -> Organization details menu item
• If logging in as a super admin
  • Go to the Admin -> Organizations menu item
  • Edit an Org
  • Make sure the org has a contact email
• Replace or Add a logo
• Click Save
• The logo should appear and no error message should be present

[jupiter007]

I was able to add and delete logos