Replace Ionicons

[don-smith]

These were included because they are the default for the InputMoment control used on the New Event form. To get them to work, I'm linking the CSS in index.html. I couldn't quickly figure out how to include them with Webpack. I'd prefer to bundle everything so I need to investigate a better icon library (FontAwesome? which is already being bundled?). I'll come back to this later.

[don-smith]

Completed. FontAwesome is included with semantic-ui-react which we're using now.