~/.bashrc: Echo bell-character after each command.

This makes urxvt set the urgent flag and notifies both tmux and
awesomewm. Quite nice for long-running scripts (installs, compiles,
whatevers).

.bashrc

#export PS1="\u [$(t | wc -l | sed -e's/ *//')] \w ($(git branch | sed 's/^\* //'))$ "
export PS1='\u \w$ '
export PROMPT_COMMAND='history -a; history -c; history -r;'
export PROMPT_COMMAND='history -a; history -c; history -r; echo -en "\a"'
export EDITOR LESS
export HISTIGNORE HISTCONTROL HISTSIZE=1000000