rustpkg: update README saying which tests pass

src/librustpkg/README.txt

@@ -1,4 +1,24 @@
-Right now (2013-04-11), only one package works, the branch of rust-sdl at:
+Right now, commands that work are "build" and "clean".
-https://github.com/catamorphism/rust-sdl/tree/new-rustpkg
 
-and only one command works, "build".
+`rustpkg build` and `rustpkg clean` should work
+
+for example:
+$ cd ~/rust/src/librustpkg/testsuite/pass
+$ rustpkg build hello-world
+... some output ...
+$ rustpkg clean hello-world
+
+-------------
+the following test packages in librustpkg/testsuite/pass:
+      * hello-world
+      * install-paths
+      * simple-lib
+      * deeply/nested/path
+      * fancy-lib
+
+   It fails on the following test packages:
+      * external-crate (no support for `extern mod` inference yet)
+
+and should fail with proper error messages
+on all of the test packages in librustpkg/testsuite/fail
+      * no-inferred-crates