Fix creating .npmignore instead of .gitignore.

This is in fact npm bug or feature - each .gitignore, even deeper one,
is changed to .npmignore upon `npm publish`.

Renamed .gitignore to different name and added item to rename.json
so it is still saved as .gitignore.

rename.json

@@ -1,4 +1,5 @@
 {
+  "gitignore-file": ".gitignore",
   "src/name.js": "src/{%= name %}.js",
   "src/name.st": "src/{%= name %}.st"
 }