Fix so copySync unlinking read only file will now work on

nodejs 0.10.40. This commit fixes #183.

lib/copy-sync/copy-file-sync.js

@@ -9,6 +9,7 @@ function copyFileSync (srcFile, destFile, options) {
 
   if (fs.existsSync(destFile)) {
     if (clobber) {
+      fs.chmodSync(destFile, parseInt('777', 8))
       fs.unlinkSync(destFile)
     } else {
       throw Error('EEXIST')