[Environment] Makes the README better.

So that it shows the Travis build badge, and gives more information
about what we're doing.
diff --git a/README.md b/README.md
index 077ba41..7831fb7 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,14 @@
 automerge-plugin
 ================
 
-Gerrit plugin to automatically merge reviews
+[![Build Status](https://travis-ci.org/criteo/automerge-plugin.svg?branch=master)](https://travis-ci.org/criteo/automerge-plugin)
+
+A [gerrit](https://code.google.com/p/gerrit/) plugin that takes care of
+automatically merging reviews when all approvals are present.
+
+Also, it introduces the concept of cross-repository reviews.
+Cross repository reviews are reviews that share a common topic, and are all
+in different gerrit repositories. They will be merged at the same time,
+when all approvals for all reviews are present, and all reviews are mergeable.
+
+Requires Gerrit 2.10 or later.