README.md in elasticsearch-api-0.4.7 vs README.md in elasticsearch-api-0.4.8

@@ -12,9 +12,16 @@
 [`elasticsearch-transport`](https://github.com/elasticsearch/elasticsearch-ruby/tree/master/elasticsearch-transport)
 library.
 
 The library is compatible with Ruby 1.8.7 or higher.
 
+The library is compatible with Elasticsearch 0.90 and 1.0 -- you have to install and use a matching version, though.
+
+The 1.0 pre-release version and the master branch are compatible with **Elasticsearch 1.0** API.
+
+To use the **Elasticsearch 0.90** API, install the **0.4.x** gem version or use the corresponding
+[`0.4`](https://github.com/elasticsearch/elasticsearch-ruby/tree/0.4) branch.
+
 ## Installation
 
 Install the package from [Rubygems](https://rubygems.org):
 
     gem install elasticsearch-api