Added a compatibility matrix to the libraries' READMEs

Closes #322
Closes #323

Author: karmi

README.md

@@ -11,14 +11,18 @@ see the <https://github.com/elasticsearch/elasticsearch-rails> project.
 
 ## Compatibility
 
-The libraries are compatible with Ruby 1.8.7 and higher.
-
-The library is compatible with Elasticsearch 0.90, 1.x and 2.x -- you have to install and use a matching version, though.
-
-The 1.x versions and the master branch are compatible with Elasticsearch 1.x and 2.x APIs.
-
-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.
+The Elasticsearch client is compatible with Ruby 1.8.7 and higher.
+Other libraries in this repository might require a more recent Ruby version.
+
+The client's API is compatible with Elasticsearch's API versions from 0.90 till current,
+just use a release matching major version of Elasticsearch.
+
+| Ruby          |   | Elasticsearch |
+|:-------------:|:-:| :-----------: |
+| 0.90          | → | 0.90          |
+| 1.x           | → | 1.x           |
+| 2.x           | → | 2.x           |
+| master        | → | master        |
 
 ## Installation
 

elasticsearch-api/README.md

@@ -9,17 +9,19 @@ The `elasticsearch-api` library provides a Ruby implementation of
 the [Elasticsearch](http://elasticsearch.org) REST API.
 
 It does not provide an Elasticsearch client; see the
-[`elasticsearch-transport`](https://github.com/elasticsearch/elasticsearch-ruby/tree/master/elasticsearch-transport)
-library.
+[`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 Ruby 1.8.7 and higher.
 
-The library is compatible with Elasticsearch 0.90, 1.x and 2.x -- you have to install and use a matching version, though.
+It is compatible with Elasticsearch's API versions from 0.90 till current,
+just use a release matching major version of Elasticsearch.
 
-The 1.x versions and the master branch are compatible with Elasticsearch 1.x and 2.x APIs.
-
-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.
+| Ruby          |   | Elasticsearch |
+|:-------------:|:-:| :-----------: |
+| 0.90          | → | 0.90          |
+| 1.x           | → | 1.x           |
+| 2.x           | → | 2.x           |
+| master        | → | master        |
 
 ## Installation
 

elasticsearch-transport/README.md

@@ -16,7 +16,7 @@ data serialization and transport.
 It does not handle calling the Elasticsearch API;
 see the [`elasticsearch-api`](https://github.com/elasticsearch/elasticsearch-ruby/tree/master/elasticsearch-api) library.
 
-The library is compatible with Ruby 1.8.7 or higher and with Elasticsearch 0.90 and 1.0.
+The library is compatible with Ruby 1.8.7 or higher and with all versions of Elasticsearch since 0.90.
 
 Features overview:
 

elasticsearch/README.md

@@ -19,14 +19,17 @@ see the <https://github.com/elasticsearch/elasticsearch-rails> project.)
 
 ## Compatibility
 
-The library is compatible with Ruby 1.8.7 and higher.
+The Elasticsearch client for Ruby is compatible with Ruby 1.8.7 and higher.
 
-The library is compatible with Elasticsearch 0.90 and 1.0 -- you have to install and use a matching version, though.
+The client's API is compatible with Elasticsearch's API versions from 0.90 till current,
+just use a release matching major version of Elasticsearch.
 
-The 1.x versions 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.
+| Ruby          |   | Elasticsearch |
+|:-------------:|:-:| :-----------: |
+| 0.90          | → | 0.90          |
+| 1.x           | → | 1.x           |
+| 2.x           | → | 2.x           |
+| master        | → | master        |
 
 ## Installation