Teacher's Classroom List now reflects most recent Edited Classroom

[shaunanoordin]

Addresses an issue brought up in #188

Issue 1: After using Edit Classroom and clicking Submit, the list of Classrooms does not update to reflect the changes. Analysis:

• Refreshing the page, however, shows that the Classroom List is properly updated.
• This indicates that the API was called correctly, but the return doesn't properly update the current state.teachers data

Solution: EDIT_CLASSROOM_SUCCESS action & reducers tweaked so that when the event triggers, the state's list of classroom is updated with the most recently (successful) edits.

@simoneduca , this is good to go. This PR can be reviewed & merged separately from #211 (i.e. 211 is not a requirement for this to be merged into edit-form)

[simoneduca]

LGTM, thank you!