remove previous selectedText if last submission errored
show full message text if last submission errored

If the last submission errored and we're displaying an the error
message, allow the message to wrap to be fully displayed.
refine state machine transitions

This addresses two concerns with the state machine transitions
introduced in 7e36804:
1) lastSuccessfulSM subscription events need to be triggered on event
firing, not state change
2) storing event information should happen when the event fires, not
based on state change

The flow should be:
- When an event fires, store the parameters for the event (link created,
text selected, error message)
- Trigger alerts for the last submission (based on new state)
- Cascade the updates to lastSuccessfulSM
- Trigger alerts if lastSuccessful state changed
continue to display tweet dialog if no shareText
explicitly quote callback functions on the SM

Calls to dynamically-generated functions on the State Machine *must* be
referenced via index-notation. This is a result of the way Google
Closure Compiler minifies the code. Similarly, the callback event names
must be quoted so the names are not mangled.