Refactor wrapper

This brings the wrapper class in line with the others.

The class is now constructed via the options passed to `#use`,
which means we don't need to change the signature of any methods,
which was not ideal.

  stack = GH::Stack.build do
    use GH::Retry, retries: 10
  end

  GH.with(stack) { GH['users/rkh'] }

Also renames the `sleep` option to `wait`.

lib/gh/retry.rb

@@ -7,29 +7,34 @@ module GH
   class Retry < Wrapper
     DEFAULTS = {
       retries: 5,
-      sleep: 1
+      wait: 1
     }
 
-    def [](key, opts = {})
-      generate_response key, fetch_resource(key, opts)
+    attr_accessor :retries, :wait
+
+    def initialize(backend = nil, options = {})
+      options = DEFAULTS.merge options
+      super backend, options
     end
 
-    def fetch_resource(key, opts = {})
-      opts = DEFAULTS.merge opts
-      retries, sleep_time = opts[:retries], opts[:sleep]
+    def fetch_resource(key)
       begin
-        retries -= 1
-        super(key)
+        decrement_retries!
+        super key
       rescue GH::Error(response_status: 404) => e
-        raise(e) unless retries_remaining?(retries)
-        sleep sleep_time
-        fetch_resource key, retries: retries, sleep: sleep_time
+        retries_remaining? or raise e
+        sleep wait
+        fetch_resource key
       end
     end
 
     private
 
-    def retries_remaining?(retries)
+    def decrement_retries!
+      self.retries = self.retries - 1
+    end
+
+    def retries_remaining?
       retries > 0
     end
   end

spec/retry_spec.rb

@@ -14,10 +14,10 @@ def fetch_resource(key)
     end
   end
 
-  before { subject.backend = not_finder.new }
+  subject { described_class.new(not_finder.new, retries: 3, wait: 0.1) }
 
   it 'retries request specified number of times' do
-    expect { subject['users/not-found', retries: 3, sleep: 0.1] }.to raise_error(GH::Error)
+    expect { subject['users/not-found'] }.to raise_error(GH::Error)
     expect(subject.backend.requests.count).to eq 3
   end