add config class and schedule

spec/config_spec.rb

@@ -0,0 +1,10 @@
+require "spec_helper"
+
+describe Periodicity::Config do
+  describe "#initialize" do
+    it "should initialize schedule with an empty array" do
+      @config = Periodicity::Config.instance
+      expect(@config.schedule).to eql([])
+    end
+  end
+end

spec/extensions/active_job_spec.rb

@@ -0,0 +1,16 @@
+require "spec_helper"
+
+class TestJob < ActiveJob::Base
+  def perform;end
+end
+
+TestJob.extend(Periodicity::Extensions::ActiveJob)
+
+describe Periodicity::Extensions::ActiveJob do
+  describe "#perform_every" do
+    it "should add job and period to schedule" do
+      TestJob.perform_every(1.second)
+      expect(Periodicity::Config.instance.schedule).to_not be_empty
+    end
+  end
+end

spec/spec_helper.rb

@@ -1,6 +1,7 @@
 require 'bundler/setup'
 Bundler.setup
 
+require 'active_job'
 require 'timecop'
 require 'periodicity'