[PATCH] Documentation of block helpers need to be updated

This patch contains changes in the documentation for the following change in the block helper behaviour:

<% form_for @something do |f| %>
   ... 
<% end %>

Should now be

<%= form_for @something do |f| %>
   
<% end %>

I have walked through the actionview directory to find all occurences of block helpers in the documentation and I have updated it according to the new situation.