move helpers to their own file

support/helpers.sh

+function error() {
+  echo " !     $*" >&2
+  exit 1
+}
+
+function mktmpdir() {
+  dir=$(mktemp -t node-$1-XXXX)
+  rm -rf $dir
+  mkdir -p $dir
+  echo $dir
+}
+
+function indent() {
+  c='s/^/       /'
+  case $(uname) in
+    Darwin) sed -l "$c";;
+    *)      sed -u "$c";;
+  esac
+}
\ No newline at end of file