Customize surveyor to accept grid_dropdowns

Required an addition of column to Response model and
a significant addition t _question_group.html.haml.
	new file:   app/helpers/surveyor_helper.rb - This file may be redundant.  It
	is supposed to override the file in Surveyor, but does not.  Copied this file
	to lib/generator and that worked.  Leave this for a while and see if there is a way
	to make it work instead of using generator.

	modified:   app/models/permitted_params_decorator.rb - add column_id to Response and
	Answer.

	new file:   app/views/partials/_question_group.html.haml - Add support for grid_dropdown.

	modified:   lib/generators/surveyor_gui/install_generator.rb - Adds migration for
	add_column_id_to_responses

	new file:   lib/generators/surveyor_gui/templates/app/helpers/surveyor_helper.rb - Overrides
	surveyor_helper.rb in Surveyor.

	new file:   lib/generators/surveyor_gui/templates/db/migrate/20140603155606_add_column_id_to_responses.rb
	adds column_id to Response.

	modified:   lib/surveyor_gui/engine.rb - Require helpers in lib/.

	new file:   lib/surveyor_gui/helpers/surveyor_helper_methods.rb - Monkey patch response_for method.
	Needed to add column_id to the select clause for responses.  This ensures there is a response for each
	combination of column_id and question_id if question_type is grid_dropdown.

	modified:   lib/surveyor_gui/models/answer_methods.rb - Add belongs_to columns.

	modified:   lib/surveyor_gui/models/column_methods.rb - duplicate some of the methods found in Surveyor
	lib/surveyor/methods/answer_methods.rb for rendering text.

	modified:   lib/surveyor_gui/models/response_methods.rb - Add belongs_to columns.