Two issues caused detection of buffers from patch filenames to fail:
  1. git uses a/some/file where cvs used some/file.
  2. (find-buffer-visiting) doesn't seem to work with relative paths.

Closes #14

README.md: Add Installation and Development sections, removing IPC::Run from Prerequisites since we're fatpacked now

Prior to this patch you could have a scenario where

- The filename in the first hunk refers to a real file
- The emacs buffer returned by (buffer-file-name) is a symlink to this file

Since (autodetect-patch-directory-root) comparse paths, this would make the
comparison fail in the wrong place, and (autodetect-patch-directory-root) would
return a wrong result

Normally the exe goes in /usr/bin and the .el files go in
/usr/share/site-lisp (or the /usr/local versions of those if you aren't
installing a package).

Fixes #11.

log-edit buffer is now called "*amend*" when amending and "*commit*" otherwise

This only works in Git, but then amending really only works in git.

According to https://en.wikipedia.org/wiki/All_rights_reserved

Emacs interface no longer displays backend output as it comes in

The emacs interface creates and populates a *commit-patch* buffer. This is meant
to stay in the background unless something goes wrong. Due to a bug in Emacs
(http://debbugs.gnu.org/cgi/bugreport.cgi?bug=17815) this buffer was getting
displayed if using commit-patch with TRAMP, even when no error has occured.

This patch asks emacs to not update this buffer with the data as it comes in.
This is fine here, and fixes the issue.

commit-patch-buffer-in-directory: Use commit-patch script from the same directory