Use more standard xdg-open for open()

dotfiles/bash/main.bashrc

 alias ll='ls -lh'
 alias lla='ls -lha'
 alias lr='ll -lhrt'
-alias open='gnome-open'
+alias open='xdg-open'
 alias diff='colordiff -u'
 alias dmesg='dmesg --time-format iso'
 alias pad4='sed -e "/./s/^/    /"'