[PATCH] doc: add README.md especially for github

[David Bremner]

Apparently README.md overrides README, so this will show up instead of
our generic README on github.

If the user is already on github, then clicking a link for more
information is not a hardship.
---
 README.md | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
 create mode 100644 README.md

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..ce579d8
--- /dev/null
+++ b/README.md
@@ -0,0 +1,15 @@
+If you're reading this on github.com, this is a read-only mirror of
+the notmuch project.
+
+For more information about the project, see
+
+  http://notmuchmail.org
+
+Please don't send us pull requests on github. If you have a feature
+branch that you want us to look at, use `git send-email` to send to
+notmuch at notmuchmail.org.
+
+For more information about contributing to the project, see
+
+
+  http://notmuchmail.org/contributing/
-- 
2.1.1