Falling back from mv to cp/rm on error.

Closes #388

lib/paperclip/storage/filesystem.rb

@@ -38,7 +38,12 @@ module Paperclip
           file.close
           file.close
           FileUtils.mkdir_p(File.dirname(path(style_name)))
           FileUtils.mkdir_p(File.dirname(path(style_name)))
           log("saving #{path(style_name)}")
           log("saving #{path(style_name)}")
-          FileUtils.mv(file.path, path(style_name))
+          begin
+            FileUtils.mv(file.path, path(style_name))
+          rescue SystemCallError
+            FileUtils.cp(file.path, path(style_name))
+            FileUtils.rm(file.path)
+          end
           FileUtils.chmod(0644, path(style_name))
           FileUtils.chmod(0644, path(style_name))
         end
         end
         @queued_for_write = {}
         @queued_for_write = {}