Does it need to get SVG height?
I try to remove follow lines, and it works.

```
// iconfont-webpack-plugin/lib/icons-to-woff.js line 52.

const iconHeight = getSvgHeight(result, filename);
if (!iconHeight) {
  return reject(new Error(`SVG font generation failed as icon "${filename}" does not have a height.`));
}

// iconfont-webpack-plugin/lib/icons-to-woff.js line 69.

/**
 * Reads the height of the svg
 *
 * @param  {String} svg      the svg content
 * @param  {String} filename the file name for error reporting
 * @return {Number}          height
 */
function getSvgHeight (svg, filename) {
  const parseSvg = /<svg[^>]+height\s*=\s*["']?(\d+)\s*(pt|px|)["']?/i.exec(svg);
  if (!parseSvg) {
    throw new Error(`could not read height for '${filename}'.`);
  }
  return parseSvg[1];
}

```

Without height property in svg is more useful for me. Because Illustrator outputs svgs without height property.

