Add: emms-tracktag wrapper for the audiotools program

http://audiotools.sourceforge.net/ provides a tool `tracktag`
which handles writing tags for several different audio formats,
including Opus. this patch provides a very basic wrapper to interface
between EMMS track info and tracktag metadata. It also configures
emms-tag-editor.el to use it for writing tags to Opus files.

Add: test.sh and test/test-all.el

Basic setup to run ert tests from the terminal using Emacs in batch
mode. This should load up only ERT, the tests in the test/ directory
and their dependencies.

Add: opus extension to emms-libtag-known-extensions

libtag works as a reader for opus files, this just ads the opus
extension to the regexp list.

1 files changed, 3 insertions, 0 deletions

diff --git a/test.sh b/test.sh
new file mode 100755
index 0000000..50547b1
--- /dev/null
+++ b/test.sh
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+emacs -Q --batch --directory="." -l ert -l test/test-all.el -f ert-run-tests-batch-and-exit