Make sure warn_and_pause reads from TTY

warn_and_pause will now read from /dev/tty, which is nice when
install-ALL.sh (or anything else) redirects stdin from a here doc,
file, etc.  Just in case install-ALL.sh also runs the installers with
stdin explicitly hooked up to /dev/tty as well.  This way, if any
installer wants to ask a question, we'll actually get to answer it.
Fix broken message
Update some installers

- clojure-mode now seems to require nrepl.el.
- emacs_chrome now has a second .el file that wants to load the
  original .el file.
- js2-mode lost its emacs24 branch.  I hope this means its main branch
  is now for Emacs 24.
Don't enable Flymake on Python buffer with no file

Ran into this when editing a Python source block inside org-mode.