Add npm support for local GH Url support

* Add basic package.json so npm can access using NPM styled GitHub url... mirror bower info
* Fix link in `bower.json` to be secure
* Add `.gitignore` so push doesn't send those files from `node_modules` and one other mentioned in `bower.json`

This adds support for `$ npm install git://github.com/github/octicons.git` to not error out from lack of package.json

See also:
* npm/npm#5284

**NOTE**: I currently skipped version bump and tag because I don't know how this is managed for this repository with the generation of the fonts

Thank you for the consideration and nice work with the icons.