Bash: undo change which removed homebrew from PATH

An earlier change removed commands in .bash_profile which explicitly
added homebrew's bin path to $PATH. I mistakenly believed that, because
that path was already in the $PATH, I didn't need to add it again in
.bash_profile. However, the normal $PATH includes homebrew's path at a
lower precedence than the system's bins, thus causing homebrew to break.