Exported Codepoints/SCSS Ignore startCodepoint Setting/emitCodepoints Values
Experiencing an issue using the latest build. Trying to hard-set the codepoints so they don't keep changing when new icons are added - icons are being used on several pseudo elements in builds and need to be statically defined.

I'm using the `startCodepoint` option in the font configuration to try and combat this, but the option appears to be completely ignored in both the codepoint export _and_ the generated CSS/SCSS. When exporting the codepoints to json (and all other formats), they appear to be starting at `61697` regardless of the `startCodepoint` override setting, then proceeding upwards. Possible that this may be related to the cause of the issue on #53?

**Option Setting**
```javascript
startCodepoint: Number('0xe900')
```

**Expected Codepoint Behavior**
```json
{
    "icon-alert": e900,
    "icon-arrow-down": e901,
    "icon-arrow-left": e902,
    "icon-arrow-right": e903,
    "icon-arrow-up": e904
}
```

**Exported Codepoints**
```json
{
    "icon-alert": 61697,
    "icon-arrow-down": 61698,
    "icon-arrow-left": 61699,
    "icon-arrow-right": 61700,
    "icon-arrow-up": 61701
}
```

**Generated Styles**
```css
.icon-alert:before {
  content: "\F101";
}

.icon-arrow-down:before {
  content: "\F102";
}

.icon-arrow-left:before {
  content: "\F103";
}

.icon-arrow-right:before {
  content: "\F104";
}

.icon-arrow-up:before {
  content: "\F105";
}
```

Using Laravel Mix, but defined webpack settings are the same. Not experiencing any issues with build, frontend display (when using exported classes) or anything else.

**Webpack Config**
```javascript
module: {
  rules: [
    {
      test: /\.font\.js/,
      use: [
        MiniCssExtractPlugin.loader,
        {
          loader: 'css-loader',
          options: {
            url: false
          }
        },
        {
          loader: 'webfonts-loader'
        }
      ]
    }
  ]
}
```

**Font Config**
```javascript
module.exports = {
  'files': [
    './icons/*.svg'
  ],
  fontName: 'thefont',
  publicPath: '/',
  classPrefix: '',
  baseSelector: '.icon',
  types: ['woff'],
  fixedWidth: false,
  normalize: true,
  fileName: '[fontname].[hash].[ext]',
  embed: false,
  scssFile: true,
  startCodepoint: Number('0xe900'),
  emitCodepoints: { fileName: '[fontname].codepoints.fonts.js', type: 'json' }
}
```

Thank you for all your hard work - this has been amazing to use and has been my favorite package as of late. Any assistance or insight you can provide would be greatly appreciated.