added spec for qrcode api

spec/api/qrcode_spec.rb

+require "spec_helper"
+
+describe WeixinAuthorize::Api::Qrcode do
+
+  it "#create_qr_scene" do
+    response = $client.create_qr_scene("123")
+    expect(response.keys).to eq(["ticket", "expire_seconds"])
+    expect(response["expire_seconds"]).to eq(1800)
+  end
+
+  it "#create_qr_limit_scene" do
+    response = $client.create_qr_limit_scene("1234")
+    expect(response.keys).to eq(["ticket"])
+  end
+
+end