make index the first param

src/index.js

@@ -3,12 +3,13 @@ import createClient from './helpers/create_client';
 import { omit } from 'lodash';
 
 export default class Elastique extends events.EventEmitter {
-  constructor(options = {}) {
-    if (!options.index) throw new Error('Must specify an index to write to');
+  constructor(index, options = {}) {
+    if (!index) throw new Error('Must specify an index to write to');
 
     super();
 
     this.ready = true;
+    this.index = index;
     this.settings = Object.assign({
       interval: '1w',
       timeout: 10000,

test/index.js

@@ -9,8 +9,7 @@ describe('Elastique class', function () {
     });
 
     it('should throw with an invalid host', function () {
-      const init = () => new Elastique({
-        index: 'elastique',
+      const init = () => new Elastique('elastique', {
         client: { host: 'nope://nope' }
       });
 
@@ -18,8 +17,7 @@ describe('Elastique class', function () {
     });
 
     it('should throw with invalid hosts', function () {
-      const init = () => new Elastique({
-        index: 'elastique',
+      const init = () => new Elastique('elastique', {
         client: { hosts: [{ host: 'localhost', protocol: 'nope' }] }
       });