Commit 2: Enabled User Input

* Added ‘event’ Template for ‘userDetails’;
  - uses JQuery to snag the ‘amount’ from the form
  - includes
      - a ‘Users.update(…);’ which increments the
        user’s ‘total’ by the ‘amount’
      - a History.insert( {…} );’ for the ‘amount’, the date, and
        adds a ‘userId’ field to the History collection
        - at this point, since the app is currently set up for only
          one user, the ‘userId’ will hold ‘this._id’, which is
          actually just the id of the event itself
        - in a later iteration when the app is set up to hold
          multiple users, History’s ‘userId’ will hold ‘this.userId’
          (i.e. foreign key) in order to associate each history
          entry with a specific user

* Changed hard-coded history data output to ‘return History.find()’
* Added !! client-side !! sorting to the history data & a limit so as
to only display 5 history events.
  - Later this limit will be shifted to the !! server-side !! so only
    the 5 most recent events will be sent to the client instead
    of all the events in the collection for any particular user

* Added ‘e.preventDefault()’ because default action is ‘submit’