Set up RSpec test framework

- Add rspec-rails to the development/test group
- Generate RSpec config (.rspec, spec_helper, rails_helper)
- Add home page request spec as a smoke test
- Stop ignoring .rspec so test config is tracked

spec/requests/pages_spec.rb

@@ -0,0 +1,12 @@
+require "rails_helper"
+
+RSpec.describe "Pages", type: :request do
+  describe "GET /" do
+    it "renders the home page" do
+      get root_path
+
+      expect(response).to have_http_status(:ok)
+      expect(response.body).to include("Characterization Tool for Git Workflows")
+    end
+  end
+end