Add symbolic link for directly including latest .js files

Hello,

I suggest to add symbolic links `dist/less.js` and `dist/less.min.js` linked to `dist/less-1.7.5.js` and `dist/less-1.7.5.min.js` for **directly including**, so that developers do not have to check the latest version and update their HTML `<script>` or bunch tasks (like `Gruntfiles.js`) after every [less/less.js](https://github.com/less/less.js) updates.

Also, less.js is built for learners and developers, right? These symbolic links should always link to the latest `.js` files, even version 2.0.0.

The pull request is attached, thanks.