Fix bogus bash binary location

lib/appearance.bash

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # colored grep
 export GREP_OPTIONS='--color=auto'

lib/history.bash

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # append to bash_history if Terminal.app quits
 shopt -s histappend
@@ -17,4 +17,4 @@ export AUTOFEATURE=true autotest
 
 function rh {
   history | awk '{a[$2]++}END{for(i in a){print a[i] " " i}}' | sort -rn | head
-}
+}

lib/preexec.bash

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # http://www.twistedmatrix.com/users/glyph/preexec.bash.txt
 # preexec.bash -- Bash support for ZSH-like 'preexec' and 'precmd' functions.