Update documentation about versions since 2.0.0

Closes #195.

Author: dadoonet

README.md

@@ -27,10 +27,13 @@ You need to install a version matching your Elasticsearch version:
 
 |       Elasticsearch    | Attachments Plugin|                                                             Docs                                                                   |
 |------------------------|-------------------|------------------------------------------------------------------------------------------------------------------------------------|
-|    master              |                   | See elasticsearch [master branch](https://github.com/elastic/elasticsearch/tree/master/plugins/mapper-attachments)                                                                                                                          |
-|    es-2.x              |                   | See elasticsearch [2.x branch](https://github.com/elastic/elasticsearch/tree/2.x/plugins/mapper-attachments)                                                                                                                          |
 |    es-2.1              |     3.1.0         | [3.1.0](https://github.com/elastic/elasticsearch-mapper-attachments/tree/v3.1.0/#version-310-for-elasticsearch-21)                  |
+|    2.1.0               |     3.1.0         | [3.1.0](https://github.com/elastic/elasticsearch-mapper-attachments/tree/v3.1.0/#version-310-for-elasticsearch-21)                  |
 |    es-2.0              |     3.0.3         | [3.0.3](https://github.com/elastic/elasticsearch-mapper-attachments/tree/v3.0.3/#version-303-for-elasticsearch-20)                  |
+|    2.0.1               |     3.0.3         | [3.0.3](https://github.com/elastic/elasticsearch-mapper-attachments/tree/v3.0.3/#version-303-for-elasticsearch-20)                  |
+|    2.0.0               |     3.0.2         | [3.0.2](https://github.com/elastic/elasticsearch-mapper-attachments/tree/v3.0.2/#version-302-for-elasticsearch-20)                  |
+|    2.0.0-beta2         |     3.0.1         | [3.0.1](https://github.com/elastic/elasticsearch-mapper-attachments/tree/v3.0.1/#version-301-for-elasticsearch-20)                  |
+|    2.0.0-beta1         |     3.0.0         | [3.0.0](https://github.com/elastic/elasticsearch-mapper-attachments/tree/v3.0.0/#version-300-for-elasticsearch-20)                  |
 |    es-1.7              |     2.7.1         | [2.7.1](https://github.com/elastic/elasticsearch-mapper-attachments/tree/v2.7.1/#version-271-for-elasticsearch-17)                  |
 |    es-1.6              |     2.6.0         | [2.6.0](https://github.com/elastic/elasticsearch-mapper-attachments/tree/v2.6.0/#version-260-for-elasticsearch-16)                  |
 |    es-1.5              |     2.5.0         | [2.5.0](https://github.com/elastic/elasticsearch-mapper-attachments/tree/v2.5.0/#version-250-for-elasticsearch-15)                  |