`render_blank` should trigger some kind of warning in development

[goatslacker]

If render_blank is called then chances are that something went wrong during rendering and we had to fallback. In development, it would be very nice and useful to surface a warning.

hypernova-ruby/lib/hypernova/batch_renderer.rb

Lines 55 to 59 in e6c6553

	def render_blank
	hash = {}
	jobs.each { |name_of_component, job| hash[name_of_component] = render_blank_html(job) }
	hash
	end