Move _all.do -> all.do and slightly update docs.

all.do's main job was to print a "nothing much to do" message after
running.  Nowadays it actually does do stuff, so we can remove the
warning, making _all.do redundant.

README.md

@@ -8,8 +8,8 @@ version, so other people have implemented different variants based on his
 published specification.
 
 This version, sometimes called apenwarr/redo, is probably the most advanced
-one, including support for parallel builds, improved logging, and helpful
-debugging features.
+one, including parallel builds, improved logging, extensive automated tests,
+and helpful debugging features.
 
 To build and test redo, run `./do -j10 test`.  To install it, run
 `DESTDIR=/tmp/testinstall PREFIX=/usr/local ./do -j10 install`.
@@ -19,6 +19,6 @@ To build and test redo, run `./do -j10 test`.  To install it, run
 - View the [documentation](https://redo.rtfd.io) via readthedocs.org
 - Visit the [source code](https://github.com/apenwarr/redo) on github
 - Discussions and support via the
-    [mailing list](https://groups.google.com/group/redo-list).
+    mailing list ([archives](https://groups.google.com/group/redo-list)).
     You can subscribe by sending any email message to
     `redo-list+subscribe@googlegroups.com` (note the plus sign).