generate bower.json

Mostly copied from https://github.com/jrburke/requirejs/issues/975

```json
{
  "name": "requirejs",
  "version": "2.1.9",
  "homepage": "http://requirejs.org",
  "authors": [
    "jrburke.com"
  ],
  "description": "A file and module loader for JavaScript",
  "main": "require.js",
  "keywords": [
    "AMD"
  ],
  "license": "new BSD, and MIT"
}
```

Also mentioned at https://github.com/bower/bower/issues/120#issuecomment-30982698