Add syslogger for production environment.

For the development environment we should just write to STDOUT, but on
production we want to write to a syslogger that we can pipe to logstash.
Move files into /model directory.
Add 'sidekiq' gem for background jobs.

For the GitHub API events we will process these as background jobs.
Update README.md to reflect generic services.
Move Rack::Cache middleware to config.ru.

Unless this becomes a problem I doubt there will be a need to actually
move this into individual Grape::API endpoints.
Update API to use with async Sidekiq workers.

For the Gear database update utilize asynchronous background jobs. The
idea here is that we're going to want to subscribe to many GitHub API
events for the Gear repositories.