Coderay breaks with embedded backticks

[vpereira]

CodeRay crashes with a comment having a quote right after backticks.

I think the culpid is here:

coderay/lib/coderay/helpers/plugin_host.rb

Lines 200 to 217 in d385021

	# Converts +id+ to a valid plugin ID String, or returns +nil+.
	#
	# Raises +ArgumentError+ for all other objects, or if the
	# given String includes non-alphanumeric characters (\W).
	def validate_id id
	case id
	when Symbol
	id.to_s
	when String
	if id[/\w+/] == id
	id.downcase
	else
	raise ArgumentError, "Invalid id given: #{id}"
	end
	else
	raise ArgumentError, "Symbol or String expected, but #{id.class} given."
	end
	end

The string

Invalid id given: '%''{version}'```

can be used to test it as described here: openSUSE/open-build-service#6960