feat(dividers): dividers passthrough className, id and style

adds functionality to passthrough style and tests for className, id
and style passthrough

[#87784030]

spec/pivotal-ui-react/divider/divider_spec.js

@@ -1,10 +1,12 @@
 require('../spec_helper');
 
+import {propagateAttributes} from '../spec_helper';
+
 describe('Divider', function() {
   var Divider;
   beforeEach(function() {
     Divider = require('../../../src/pivotal-ui-react/dividers/dividers').Divider;
-    React.render(<Divider/>, root);
+    React.render(<Divider className='test-class' id='test-id' style={{opacity: '1'}}/>, root);
   });
 
   afterEach(function() {
@@ -15,6 +17,7 @@ describe('Divider', function() {
     expect('hr').toHaveClass('divider-alternate-1');
   });
 
+  propagateAttributes('hr', {className: 'test-class', id: 'test-id', style: {opacity: '1'}});
   describe('when large is set to true', function() {
     beforeEach(function() {
       React.render(<Divider size="large"/>, root);

src/pivotal-ui-react/dividers/dividers.js

@@ -1,6 +1,6 @@
 var React = require('react');
 var types = React.PropTypes;
-var classnames = require('classnames');
+import {mergeProps} from '../../../src/pivotal-ui-react/helpers/helpers';
 
 var DividerProps = {
   propTypes: {
@@ -37,18 +37,18 @@ var Divider = React.createClass({
   mixins: [DividerProps],
 
   render() {
-    var {inverse, size, className, ...others} = this.props;
-    var classes = classnames(
-      className,
+    var {inverse, size, ...others} = this.props;
+    var dividerClass =
       {
         'divider-1': inverse && size !== 'large',
         'divider-2': inverse && size === 'large',
         'divider-alternate-1': !inverse && size !== 'large',
         'divider-alternate-2': !inverse && size === 'large'
-      }
-    );
+      };
 
-    return <hr {...others} className={classes}/>;
+    const props = mergeProps(others, {className: dividerClass});
+
+    return <hr {...props}/>;
   }
 });