unix systems only

Sync the files between a local directory and a remote directory.

Currently can upload new files, and update existing ones, and delete files from remote directory.

• (削除) add deletion (削除ここまで)
• (削除) update files (削除ここまで)
• (削除) changelog.txt (削除ここまで)

compile:

g++ server.cpp -o server
g++ client.cpp -o client