support for removing url_cache

appendix/purge_cache.lua

@@ -3,7 +3,15 @@ require 'pl'
 CACHE_DIR="cache"
 TTL = 3600 * 24
 
-local files = dir.getfiles(CACHE_DIR, "*.png")
+local files = {}
+local image_cache = dir.getfiles(CACHE_DIR, "*.png")
+local url_cache = dir.getfiles(CACHE_DIR, "url_*")
+for i = 1, #image_cache do 
+   table.insert(files, image_cache[i])
+end
+for i = 1, #url_cache do 
+   table.insert(files, url_cache[i])
+end
 local now = os.time()
 for i, f in pairs(files) do
    if now - path.getmtime(f) > TTL then