For the record if you hack the lite.bundle.js and replace

c.default.createElement("button",{className:"bpw-button ",onClick:this.handleButtonClick},this.props.label)

with this

c.default.createElement("button",{className:"bpw-button "+this.props.label.toLowerCase().trim().replace(/[^\w\s-]/g, '').replace(/[\s_-]+/g, '-').replace(/^-+|-+$/g, ''),onClick:this.handleButtonClick},this.props.label)

this will slugify the label of the button and add it as a class to the button.