Add support for per-project settings

This allows you to more easily conform to a particular project's style guidelines without affecting your main config.
For instance, if you had an unreasonable project lead who demanded 3-width indentation and spaces around everything you could have your sublime project look like this:
```
{
  "folders": [
    {
      "path": "."
    }
  ],
  "settings": {
    "tab_size": 3,
    "translate_tabs_to_spaces": true,
    "jsbeautify": {
      "space_in_paren": true,
      "indent_size": 3,
      "jslint_happy": true,
      "brace_style": "expand",
      "break_chained_methods": true,
      "indent_with_tabs": false,
      "space_before_conditional": true
    }
  }
}
```