Break TMPDIR setup out into it's own file

shell/env.sh

@@ -33,9 +33,3 @@ path_prepend "$HOME/bin"
 
 # Add dotfiles' bin directory to PATH
 path_prepend "$DOTBIN"
-
-# Ensure TMPDIR is the same for local and remote ssh logins
-if [[ $TMPDIR == "/var/folders/"* ]] || [[ $TMPDIR == "" ]]; then
-  export TMPDIR="/tmp/user-$USER"
-  mkdir -p "$TMPDIR"
-fi