bugfix: allow installing in path containing spaces
bugfix: allow installing in path containing spaces

bin/modernish:
- Since commit 2ccdc2a0, installing to a directory prefix
  containing spaces or other non-shellsafe characters is broken
  because the installer inserts the value for the variable
  assignment directly into the script. Fix by shellquoting the
  value first if needed.
  (Pathnames containing spaces occasionally happen without user
  intervention on weird systems, e.g. when installing in the user's
  home directory on Cygwin or Interix, which could be something
  like "/dev/fs/C/Documents and Settings/Martijn Dekker".)

modernish/modernish