v0.6.0

• Add :prompt() text decorator.
• Notify when trying to send to a terminal that hasn't been started yet.
• Available text decorators by name can be configured in config.text_decorators.
• .select() can take a single function instead of a table of callbacks.
• .select() to fast-forward if single terminal and single default callback
• Add .select_started() function to select only among started terminals.
• Add new meta table settings for custom user data.