Add Job#save to save job info to DB

spec/job_spec.rb

@@ -25,4 +25,19 @@ describe Crono::Job do
       expect(job.description).to be_eql("Perform TestJob every 2 days")
     end
   end
+
+  describe "#save" do
+    it "should save new job to DB" do
+      expect(Crono::CronoJob.where(job_id: job.job_id)).to_not exist
+      job.save
+      expect(Crono::CronoJob.where(job_id: job.job_id)).to exist
+    end
+
+    it "should update saved job" do
+      job.last_performed_at = Time.now
+      job.save
+      @crono_job = Crono::CronoJob.find_by(job_id: job.job_id)
+      expect(@crono_job.last_performed_at).to be_eql(job.last_performed_at)
+    end
+  end
 end