title: Copy files with Yeoman generator doesn't work
body: <p>I'm developing my own generator with Yeoman. When I try to copy some files, nothing happens. No error, the process continues until it reach the end, but no files are copied. The generator has a /templates dir with a bunch of html files, each file has a few html lines, at the moment quite simple stuff. 
  This is my copy method:</p>
  
  <pre><code>copyMainFiles: function(){
      console.log('copyMainFiles dir:' + process.cwd() + '+++++');
      console.log('file exists? '+fs.existsSync('_footer.html') );
      this.copy("_footer.html",  "app/footer.html");
      console.log('footer copied');
      this.copy("_gruntfile.js", "Gruntfile.js");
      console.log('gruntfile copied');
      this.copy("_package.json", "package.json");
      console.log('package copied');
      this.copy("_main.css",     "app/css/main.css");
      console.log('main.css copied');
  
      var context = { 
          site_name: this.appName 
      };
  
      console.log('all files copied');
      //template method makes the replacement and then copy
      this.template("_header.html", "app/header.html", context);
      console.log('header template processed');
  },
  </code></pre>
  
  <p>this is the console output:</p>
  
  <p>$ yo trx</p>
  
  <p>method 1 just ran</p>
  
  <p>method 2 just ran</p>
  
  <p>? What is your app's name ?
  Kosheen</p>
  
  <p>? Would you like to generate a demo section ? Yes</p>
  
  <p>all dirs created</p>
  
  <p>copyMainFiles dir:C:\cygwin\Applications\MAMP\htdocs\prueba-trx+++++</p>
  
  <p>file exists? false</p>
  
  <p>footer copied</p>
  
  <p>gruntfile copied</p>
  
  <p>package copied</p>
  
  <p>main.css copied</p>
  
  <p>all files copied</p>
  
  <p>header template processed</p>
  
  <p>running npm</p>
  
  <p>and that's it. Never returns to system prompt.</p>
  
  <p>Besides the fact that fs.existsSync returns false (the file exists: htdocs\generator-trx\generators\app\templates_footer.html ), if I try to copy a non-existent file I get the typical error. </p>
  
  <p>Folders are created previously with no issue. There's a .yo_rc.json file with {} in the root of the destination folder. The Yeoman version is 1.4.8, working on Windows 7. </p>
  
  <p>Is copy() the proper way to do this or is no longer valid? How can I copy a simple file in this scenario?</p>