Refactored almost everything

There are some major fundemental changes with the library. For instance,
now we will be treating the Wellness::System similar to how we treat
Rack.

  system = Wellness::System.new('some_system')
  system.use(Wellness::Services::RedisService, { ... })
  system.use(Wellness::Services::PostgresService, { ... })

  config.middleware.insert_before(
    '::ActiveRecord::QueryCache',
    'Wellness::Middleware',
    system
  )

The Wellness::Services::Base hasn't changed too much, #check is still
working just find, #passed_check is deprecated, #failed_check is
deprecated. Currently they will just #warn when it is used.
Updated the README
Pass an array of objects to Report

Took the advice of @nateklaiber and made the Report less aware of what
defines 'HEALTHY' and passed in an Array of Services and Details.
Added options to be passed into a Detail

Updated README documentation
Merge pull request #4 from warmwaffles/mj/refactor

Major version bump