fix you cant download some large map file

[bklol]

add memory_limit set ，so your php want give you like "Fatal error: Allowed memory size of xxxxxxx bytes exhausted"

[naydef]

Thanks for the pull request. Changes seem reasonable, although I believe filenames containing hyphen is a bad idea generally.

Also can you change the comment which mentions memory limit? Make It match what the actual limit is (or remove it).