add 'String#%'.

mrbgems/mruby-sprintf/mrblib/string.rb

+class String
+  def %(args)
+    if args.is_a? Array
+      sprintf(self, *args)
+    else
+      sprintf(self, args)
+    end
+  end
+end

mrbgems/mruby-sprintf/test/sprintf.rb

-##
-# Kernel#sprintf Kernel#format Test
+#assert('Kernel.sprintf') do
+#end
 
+assert('String#%') do
+  assert_equal "one=1", "one=%d" % 1
+  assert_equal "1 one 1.0", "%d %s %3.1f" % [ 1, "one", 1.01 ]
+  assert_equal "123 < 456", "%{num} < %<str>s" % { num: 123, str: "456" }
+end