Add SSH Support
You can now index files remotely using SSH:

* FS URL: `/tmp3`
* Server: `mynode.mydomain.com`
* Username: `username`
* Password: `password`
* Protocol: `ssh` (default to `local`)
* Update Rate: every hour (60 * 60 * 1000 = 3600000 ms)
* Get only docs like `*.doc`, `*.xls` and `*.pdf`

```sh
curl -XPUT 'localhost:9200/_river/mysshriver/_meta' -d '{
  "type": "fs",
  "fs": {
	"url": "/tmp3",
	"server": "mynode.mydomain.com",
	"username": "username",
	"password": "password",
	"protocol": "ssh",
	"update_rate": 3600000,
	"includes": [ "*.doc" , "*.xls", "*.pdf" ]
  }
}'
```

Closes #12.