Minor enhancement to README

[ElTopo]

The first sentence
"This is a simple KeePass Plugin that saves a backup of your Password-Database to a backup location..."
would be better if it's:
"This is a simple KeePass Plugin that saves a backup of your Password-Database to several pre-defined backup locations..."

I think this is a very good selling point to a potential new user who's reading the README. Just earlier today when I recommended this plugin to a guy the first question he asked was "only 1 backup location?" In fact, KPSimpleBackup is capable to save backups to several locations, and that's the reason I love to use it. I have 4 locations to save database backups: a different folder (than the default working database folder) on my SSD drive, a folder on an SD card inserted on my computer, and 2 folders on my 2 samba servers.