Remove unused GitHub endpoint wrappers

lib/github/issues.rb

-module Github
-  class Issues
-    attr_reader :owner, :repo
-
-    def initialize(owner, repo)
-      @owner = owner
-      @repo  = repo
-    end
-
-    def fetch
-      Collection.new(issues_url).fetch(state: :all, sort: :created, direction: :asc, per_page: 10)
-    end
-
-    private
-
-    def issues_url
-      "/repos/#{owner}/#{repo}/issues"
-    end
-  end
-end

lib/github/labels.rb

-module Github
-  class Labels
-    attr_reader :owner, :repo
-
-    def initialize(owner, repo)
-      @owner = owner
-      @repo  = repo
-    end
-
-    def fetch
-      Collection.new(labels_url).fetch
-    end
-
-    private
-
-    def labels_url
-      "/repos/#{owner}/#{repo}/labels"
-    end
-  end
-end

lib/github/milestones.rb

-module Github
-  class Milestones
-    attr_reader :owner, :repo
-
-    def initialize(owner, repo)
-      @owner = owner
-      @repo  = repo
-    end
-
-    def fetch
-      Collection.new(milestones_url).fetch
-    end
-
-    private
-
-    def milestones_url
-      "/repos/#{owner}/#{repo}/milestones"
-    end
-  end
-end

lib/github/pull_requests.rb

-module Github
-  class PullRequests
-    attr_reader :owner, :repo
-
-    def initialize(owner, repo)
-      @owner = owner
-      @repo  = repo
-    end
-
-    def fetch
-      Collection.new(pull_requests_url).fetch(state: :all, sort: :created, direction: :asc)
-    end
-
-    private
-
-    def pull_requests_url
-      "/repos/#{owner}/#{repo}/pulls"
-    end
-  end
-end

lib/github/releases.rb

-module Github
-  class Releases
-    attr_reader :owner, :repo
-
-    def initialize(owner, repo)
-      @owner = owner
-      @repo  = repo
-    end
-
-    def fetch
-      Collection.new(releases_url).fetch
-    end
-
-    private
-
-    def releases_url
-      "/repos/#{owner}/#{repo}/releases"
-    end
-  end
-end