closes #5966

Spring is the recommended application preloader for rails

* Dropped all references to Resque
* Moved all jobs under app/workers since that's the Sidekiq convention
* Renamed Jobs module to Worker to match new location
* Adapted all jobs to Sidekiq
* Replaced all enqueue calls with perform_async
* Dropped Resque hacks from specs and features, replaced with
  sidekig/testing in RSpec and sidekig/testing/inline in Cucumber
* Updated scripts to start a Sidekiq server
* Inline Sidekiq sinatra app
* Let Sidekiq create the actual Redis instance
* Workaround already initialized constant warnings in service models
* Resolved ToDo in one job definition by creating proper exception clases
  for some errors in receiving posts
* Added sidekiq section to configuration to make it completly
  configurable to the user
* Add Sidekiq middleware for clean backtraces
* Delay HttpMulti retry to give offline pods a chance to come back up
* Do not retry on GUID already taken and alike errors
* Be graceful about deleted posts in GatherOEmbedData

add unicorn back in.  only use one worker process for now.  also, move chrome_frame middleware into the correct load path in lib. [ci skip]

This reverts commit 641cedf3.

Revert "Merge pull request #2663 from torrancew/with_unicorn"

This reverts commit 2a2efd09, reversing
changes made to 78978f05.

we find a better way to reimpliment it in a  more sane way

Added Foreman gem.  Run Diaspora using `foreman start` (will start everything except mySQL.  Passing in a -p flag will let you specifiy the port.  Also: I took single_process_mode out of app config and made it an environment variable.  If you want to boot a lightweight server, run `SINGLE_PROCESS=true rails s`.