Remove extra colon from "X-" properties

Pulled from rubyredrick#5.

Author: tfausak

lib/ri_cal/component.rb

@@ -220,7 +220,7 @@ def export_prop_to(export_stream, name, prop) #:nodoc:
     def export_x_properties_to(export_stream) #:nodoc:
       x_properties.each do |name, props|
         props.each do | prop |
-          export_stream.puts("#{name}:#{prop}")
+          export_stream.puts("#{name}#{prop}")
         end
       end
     end