Adds "Type to sign" support to Signature Pad.

We've added type to sign functionality to the signature pad.

Requires setting the following params:

```javascript
options {
  enabledThypeToSign: true,
  inputSelector: "#selector-for-input",
  maxFontSize: "30",  // Defaults to 300 pt.
  fontface: "Arial" // Defaults to Helvetica
}
```