Add support for guard and spring

guard encourages TDD behaviour through development iterations which
include continuous testing.

Coupling this with spring eliminates the cost of continually loading
gems into a fresh environment every time the tests are run.

Guardfile

@@ -0,0 +1,64 @@
+#!/usr/bin/ruby
+#
+# More info at https://github.com/guard/guard#readme
+
+guard_opts = {
+  all_on_start:   true,
+  all_after_pass: true,
+  cmd: 'spring rspec'
+}
+
+def model_specs       ; "spec/models"       end
+
+def model_spec(model)
+  "spec/models/#{model}_spec.rb"
+end
+
+def all_testunit_tests
+  [
+    model_tests,
+    controller_tests,
+    helper_tests,
+    integration_tests,
+  ]
+end
+
+def all_specs
+  [
+    model_specs,
+  ]
+end
+
+def startup_guards
+  watch(%r{^Gemfile$})                      { yield }
+  watch(%r{^Gemfile.lock$})                 { yield }
+  watch(%r{^config/routes.rb$})             { yield }
+  watch(%r{^config/application\.rb$})       { yield }
+  watch(%r{^config/environment\.rb$})       { yield }
+  watch(%r{^config/environments/.+\.rb$})   { yield }
+  watch(%r{^config/initializers/.+\.rb$})   { yield }
+  watch(%r{^db/schema\.rb$})                { yield }
+  watch(%r{^spec/spec_helper\.rb$})         { yield }
+end
+
+def rspec_guards
+  watch(%r{^spec/factories/.+\.rb$})        { all_specs }
+  watch(%r{^spec/.+_spec\.rb$})
+  watch(%r{^app/(.+)\.rb$})                 { |m| "spec/#{m[1]}_spec.rb" }
+end
+
+group :rspec do
+  guard 'rspec', guard_opts do
+    #startup_guards { all_specs }
+    rspec_guards
+    #all_specs
+  end
+end
+
+# group :bundler do
+#   guard 'bundler' do
+#     watch('Gemfile')
+#     # Uncomment next line if Gemfile contain `gemspec' command
+#     # watch(/^.+\.gemspec/)
+#   end
+# end