update to 0.90
Replace deprecated method:

```
Closeables.closeQuietly(is);
```

by
 ```
Closeables.close(is, true);
```

Closes #28.
prepare release elasticsearch-river-couchdb-1.2.0
prepare for next development iteration
Create CONTRIBUTING.md
Support for changing id via script
I know two ways to change id.

1. The simply way:

 ```
 "script": "ctx.id = ctx.doc._id = ctx.doc.new_id;"
 ```

2. Associate the _id mapping with a path:

 ```
 {
     "mappings": {
         "my_type": {
             "_id": {"path": "new_id"},
         }
     }
 }
 ```

 and set id to null:
 ```
 "script": "ctx.id = ctx.doc._id = null;"
 ```

But in both cases a river doesn't change id keeping it always as the couchdb's id.

Closes #33.
Timeout if no heartbeat received on time.

Add a read timeout so that the case where no heartbeat is received from
CouchDB is caught. The default value for read timeout allows for three
heatbeats to be missed. Also allow heartbeat and read timeout values to be
configured.

Closes #36.
Describe how to start at a particular CouchDB sequence

Add documentation describing how to have the CouchDB river start at a particular sequence number rather than from the beginning.

Closes #34
Indexing CouchDB attachments
Relative to #25