Allow a proposal to be created with a Subtitle and Difficulty Level.

When a proposal is being submitted, we want to allow the submitter to
fill out the form once with all the required data. This change unifies
the forms for both editing and creating proposals. This allows us to
ensure that features are added in parallel to both workflows.

We also reduce the number of duplicate lines by removing duplicates
from the new.html.haml file.

We also increase the column size in css to have both pages show the
same width forms.

spec/features/proposal_spec.rb

@@ -114,7 +114,7 @@ feature Event do
       select('Example Event Type', from: 'event[event_type_id]')
 
       fill_in 'event_abstract', with: 'Lorem ipsum abstract'
-      click_link 'description_link'
+      click_link 'Do you require something special?'
       fill_in 'event_description', with: 'Lorem ipsum description'
 
       click_button 'Create Proposal'