Add unit test

spec/config_spec.cr

@@ -0,0 +1,14 @@
+require "./spec_helper"
+
+describe Config do
+	it "creates config if it does not exist" do
+		tempfile = File.tempfile "mango-test-config"
+		config = Config.load tempfile.path
+		File.exists?(tempfile.path).should be_true
+		tempfile.delete
+	end
+	it "correctly loads config" do
+		config = Config.load "spec/asset/test-config.yml"
+		config.port.should eq 3000
+	end
+end