Use groovy as default scripting language

As for elasticsearch 1.3.0, `groovy` is the new default scripting language.

Related to: elastic/elasticsearch#6233

Closes #61.
(cherry picked from commit 170a2cd)

README.md

@@ -98,7 +98,7 @@ change (for example, **ctx.doc** will refer to the document, or **ctx.deleted**
 Any other [script language supported by Elasticsearch](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/modules-plugins.html#scripting) 
 may be used by setting the `script_type` parameter to the appropriate value. 
 
-If unspecified, the default is `mvel`. 
+If unspecified, the default is `groovy`. 
 See [Scripting documentation](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/modules-scripting.html) for details. 
 
 The **ctx.doc** can be changed and its value can will be indexed (assuming its not a deleted change). 

pom.xml

@@ -62,6 +62,12 @@
             <scope>test</scope>
         </dependency>
 
+        <dependency>
+            <groupId>org.codehaus.groovy</groupId>
+            <artifactId>groovy-all</artifactId>
+            <version>2.3.2</version>
+            <scope>test</scope>
+        </dependency>
 
         <dependency>
             <groupId>org.elasticsearch</groupId>

src/main/java/org/elasticsearch/river/couchdb/CouchdbRiver.java

@@ -140,7 +140,7 @@ public CouchdbRiver(RiverName riverName, RiverSettings settings, @RiverIndexName
             }
 
             if (couchSettings.containsKey("script")) {
-                String scriptType = "mvel";
+                String scriptType = "groovy";
                 if(couchSettings.containsKey("script_type")) {
                     scriptType = couchSettings.get("script_type").toString();
                 }