Don't "open in Downloads from Chrome" in `in-cwd`

Maybe made sense at some point, but it's rarely where I want to start a
shell these days.
Adds ~/.config/in-cwd.default link as default dir

If the shell's current directory can't be determined, cd to wherever
that link points.
Fix `git bdm` (branch delete merged) selection

Don't delete any branches without slashes in their names.  (e.g. our
normal stages: `dev`, `release-candidate`, and `master`)
Use `zeus` if possible for naming gem directories
Fill out `zsh_directory_name` handler

Handle all calling environments:
- `n` = name to directory (previously handled)
- `d` = directory to name (unimplemented)
- `c` = completion (added)
- ? = invocation error