Adds :focus option to various rails helpers.

Makes this code:

	<%= text_field :user, :name, :focus => true %>

generate this:	

	<input id="user_name" name="user[name]" size="30" type="text" />
	<script type="text/javascript">
	  //<![CDATA[
	  $('user_name').focus()
	  //]]>
	</script>
	
### Installation ###
	
	./script/plugin install http://svn.depixelate.com/plugins/focus_fu

### Supported helpers ###
text_field 
password_field
file_field
text_area
check_box
radio_button
text_field_tag
password_field_tag
file_field_tag
text_area_tag
check_box_tag
radio_button_tag
select
select_tag

### Usage ###

Add :focus => true to the end of a supported Rails helper.
	
### Examples ###

	<%= text_field :user, :name, :focus => true %>
	<%= text_field_tag :user_name, nil, :focus => true %>
	<%= select :post, :category, %w(rails python), :focus => true %>
	
### Known Issues ###

The check_box form helper does not work when used in the form_for format.

	<% form_for :user, :url => users_path do |f| %>
	   <%= f.check_box :admin, :focus => true %>        # doesn't work
	   <%= check_box :user, :admin, :focus => true %>   # works
	<% end %>