Fit issue 240 by using slug to find content-type

export.rb exports targets with
field_attributes['target'] = target_klass._parent.slug
but import imports it with:
target_content_type = site.content_types.where(:name => association.target).first

this fails if one uses capitalized names for Models.
i changed the default.zip to contain a site yaml with capitalized
Model-Names too.

lib/locomotive/import/content_types.rb

@@ -189,7 +189,7 @@ module Locomotive
           content = content._parent.reload.contents.find(content._id) # target should be updated
 
           associations.each do |association|
-            target_content_type = site.content_types.where(:name => association.target).first
+            target_content_type = site.content_types.where(:slug => association.target).first
 
             next if target_content_type.nil?
 
@@ -240,4 +240,4 @@ module Locomotive
 
     end
   end
-end
+end