Set key prop on CheckboxGroupInputItem

[jaytula]

The key prop is missing in the mapping to CheckboxGroupInputItem in choices.map. This results in console.warn. This can be seen in the JavaScript console of simple example app after clicking the Edit on any of the Posts.

Warning: Each child in a list should have a unique "key" prop.

Check the render method of `CheckboxGroupInput`. See https://fb.me/react-warning-keys for more information.
    in CheckboxGroupInputItem (created by CheckboxGroupInput)
    in CheckboxGroupInput (created by PostEdit)
    in div (created by FormInput)
    in FormInput (created by WithStyles(FormInput))
    in WithStyles(FormInput) (created by FormTab)
    in span (created by FormTab)

[djhi]

Good catch! Thanks :)