FIX: cleanup old letter avatars if needed

FEATURE: use image magick version as a key for letter avatars

spec/components/letter_avatar_spec.rb

@@ -0,0 +1,15 @@
+require 'spec_helper'
+require 'letter_avatar'
+
+describe LetterAvatar do
+  it "can cleanup correctly" do
+    path = LetterAvatar.cache_path
+
+    FileUtils.mkdir_p(path + "junk")
+    LetterAvatar.generate("test", 100)
+
+    LetterAvatar.cleanup_old
+
+    Dir.entries(File.dirname(path)).length.should == 3
+  end
+end