Better invocation of bash, BSD workarounds

Using `/bin/bash` to invoke bash is effective, but does not allow for
flexability. `/usr/bin/env bash` will load bash from the PATH. This
allows for the user to set the version of bash.

As for the BSD replacements, I basically detect the presence of GNU
versions of the coreutils, and if they are present, create functions
to use them in place of the BSD versions

Helps fix issue jneen#5

bin/balls

@@ -1,4 +1,18 @@
-#!/bin/bash
+#!/usr/bin/env bash
+
+which gsed >/dev/null && sed() {
+ gsed $@
+}
+which greadlink >/dev/null && readlink() {
+ greadlink $@
+}
+which gmkfifo >/dev/null && mkfifo() {
+ gmkfifo $@
+}
+which gcat >/dev/null && cat() {
+ gcat $@
+}
+
 BALLS_LIB=$(dirname $0)/../lib
 BALLS_LIB=$(readlink -f "$BALLS_LIB") # expand the ../
 

bin/esh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 BALLS_LIB=$(readlink -f $(dirname $0)/../lib)
 
 shopt -s extglob

lib/balls.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 [[ -z "$BALLS_LIB" ]] && BALLS_LIB=.
 
 [[ -z "$BALLS_CONF" ]] && BALLS_CONF=./config.sh

lib/cgi.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # /var/www/cgi-bin/balls.sh
 [[ -z "$BALLS_CONFIG" ]] && BALLS_CONFIG=$PWD/config.sh
 

lib/http.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 http::parse_request() {
  http::read req_line

lib/model.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 [[ -z "$BALLS_DB_CREDENTIALS" ]] && BALLS_DB_CREDENTIALS=''
 [[ -z "$BALLS_DB" ]] && BALLS_DB='balls'

lib/router.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 balls::define_route() {
  local verb=$1; shift

lib/server.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 _hash() {
  echo $$.$(date +'%s.%N').$RANDOM

lib/util.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 stderr() {
  echo "$@" >&2
 }

lib/view.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 esh=$(readlink -f $BALLS_LIB/../bin/esh)
 render::esh() {
  local view="$BALLS_VIEWS/$1"