"Time spent so far" on task#show should update during the AJAX receipt of a new interval

[ethanp]

THIS IS WRONG

This will be a bit more work than I thought

1. modify intervals_controller.create_from_ajax to return the extra data instead of just

   L59: render @interval

   basically, it should instead be

   L59: render interval_data

   where _interval_data.html.haml renders the @interval as exists, but also returns a

   %p#time-spent-so-far new_time_spent_so_far

2. modify recordButtonPressed in tasks.js to utilize the extra data...waitaminute, see below

[ethanp]

I think all I have to do is add something along the lines of

"time-spent-so-far" :"<%= interval.task.time_spent_so_far %>",

to _interval.json.erb

[ethanp]

it still doesn't do anything when you delete an interval via ajax though...which is now #115