Fix syntax error in example [ci skip]

Author: parkr

README.md

@@ -33,7 +33,7 @@ Mercenary.program(:jekyll) do |p|
   p.command(:new) do |c|
     c.syntax "new PATH" # do not include the program name or super commands
     c.description "Creates a new Jekyll site scaffold in PATH"
-    c.option 'blank', '--blank', 'Initialize the new site without any content."
+    c.option 'blank', '--blank', 'Initialize the new site without any content.'
 
     c.action do |args, options|
       Jekyll::Commands::New.process(args, blank: options['blank'])