do not expand paths given by shell

do not expand paths given by shell

Shells already expand '~' before the executables see it, and
relative paths inside symlinks can get set incorrectly to the
actual directory name, and not the (usually desired) symlink
name for things like Capistrano.

Since our paths are now unexpanded, we must now check the
"working_directory" directive and raise an error if the user
specifies the config file in a way that makes the config file
unreloadable.