to prevent potential phishing attacks.

More info here: https://mathiasbynens.github.io/rel-noopener

Fixes an issue whereby those tokens are passed in but not used and instead
converse attempts to restore the session (and then totally ignores the tokens
when it fails).

Makes sense to me that you'd want your passed in tokens to be used always, even
when there are restorable tokens.

Not in the onAdded handler.

Otherwise it gets debounced for multiple instances and certain chat boxes will
then not get shown.

Don't call trimChats when the box is minimized or maximized, instead call it
only when the minimized chats toggle appears or disappears, since that's the
element that adds/removes space.

Also, a fix. 'onShow' has been renamed to 'onMaximized'

updates #443