Add support for className and style in options

Using the default optionRenderer, specifying `style` or
`className` means the style/class  gets applied at the same
level as `.Select-option`

Closes JedWatson#44

src/Option.js

@@ -1,4 +1,5 @@
 var React = require('react');
+var classes = require('classnames');
 
 var Option = React.createClass({
 	propTypes: {
@@ -14,11 +15,12 @@ var Option = React.createClass({
 	render: function() {
 		var obj = this.props.option;
 		var renderedLabel = this.props.renderFunc(obj);
+		var optionClasses = classes(this.props.className, obj.className);
 
 		return obj.disabled ? (
-			<div className={this.props.className}>{renderedLabel}</div>
+			<div className={optionClasses}>{renderedLabel}</div>
 		) : (
-			<div className={this.props.className}
+			<div className={optionClasses} style={obj.style}
 				onMouseEnter={this.props.mouseEnter}
 				onMouseLeave={this.props.mouseLeave}
 				onMouseDown={this.props.mouseDown}

test/Select-test.js

@@ -907,6 +907,40 @@ describe('Select', function() {
 		});
 	});
 
+	describe('with styled options', function () {
+
+		beforeEach(function () {
+
+			options = [
+				{ value: 'one', label: 'One', className: 'extra-one' },
+				{ value: 'two', label: 'Two', className: 'extra-two' },
+				{ value: 'three', label: 'Three', style: { fontSize: 25 } }
+			];
+
+			instance = createControl({
+				options: options
+			});
+		});
+
+		it('uses the given className for an option', function () {
+
+			clickArrowToOpen();
+			expect(React.findDOMNode(instance).querySelectorAll('.Select-option')[0], 'to have attributes',
+				{
+					class: 'extra-one'
+				});
+		});
+
+		it('uses the given style for an option', function () {
+
+			clickArrowToOpen();
+			expect(React.findDOMNode(instance).querySelectorAll('.Select-option')[2], 'to have attributes',
+				{
+					style: { 'font-size': '25px' }
+				});
+		});
+	});
+
 	describe('with allowCreate=true', function () {
 
 		beforeEach(function () {