Add --rcfile (-R) option

TODO: Connect option to RCFile class to set custom file path. (#19)

lib/twurl/cli.rb

@@ -70,6 +70,7 @@ def parse_options(args)
             quiet
             disable_ssl
             request_method
+            rcfile
             help
             version
           end
@@ -232,6 +233,12 @@ def request_method
         end
       end
 
+      def rcfile
+        on('-R', '--rcfile [path]', 'Path to RC file (default: ~/.twurlrc)') do |rcfile|
+          options.rcfile = rcfile
+        end
+      end
+
       def help
         on_tail("-h", "--help", "Show this message") do
           CLI.puts self

test/cli_test.rb

@@ -150,4 +150,17 @@ def test_setting_host_updates_to_requested_value
     end
   end
   include HostOptionTests
+
+  module RCFileTests
+    def test_setting_rcfile_uses_custom_rcfile
+      custom_rcfile = '/tmp/rcfile'
+      assert Twurl::RCFile.file_path != custom_rcfile
+
+      [['-R', custom_rcfile], ['--rcfile', custom_rcfile]].each do |option_combination|
+        options = Twurl::CLI.parse_options(option_combination)
+        assert_equal custom_rcfile, options.rcfile
+      end
+    end
+  end
+  include RCFileTests
 end