Add Crono.config

spec/config_spec.rb

@@ -3,7 +3,7 @@ require "spec_helper"
 describe Crono::Config do
   describe "#initialize" do
     it "should initialize schedule" do
-      @config = Crono::Config.instance
+      @config = Crono.config
       expect(@config.schedule).to be_a(Crono::Schedule)
     end
   end

spec/performer_proxy_spec.rb

@@ -6,7 +6,7 @@ end
 
 describe Crono::PerformerProxy do
   it "should add job and period to schedule" do
-    expect(Crono::Config.instance.schedule).to receive(:add).with(TestJob, kind_of(Crono::Period))
+    expect(Crono.config.schedule).to receive(:add).with(TestJob, kind_of(Crono::Period))
     Crono.perform(TestJob).every(2.days, at: "15:30")
   end
 end