ToggleClass problem

$(document).ready(function(){

$('.showBtn').click(function(e){
e.preventDefault();
$('.collapse-content').toggleClass('active-collapse');

});

});

<!DOCTYPE html>
<html>
<head>
	<title>fuck yeah!</title>
	<link rel="stylesheet" type="text/css" href="style.css">
	<link rel="stylesheet" type="text/css" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
</head>
<body>


<div class="container-fluid">
	<div class="row">
		<div class="col-md-4"></div>
		<div class="col-md-4"></div>
		<div class="col-md-4"></div>
		<div class="col-md-4"></div>
		<div class="col-md-4"></div>
		<div class="col-md-4"></div>
		<div class="collapse-content">
		<div class="col-md-4"></div>
		<div class="col-md-4"></div>
		<div class="col-md-4"></div>
		<div class="col-md-4"></div>
		<div class="col-md-4"></div>
		<div class="col-md-4"></div>
		<div class="col-md-4"></div>
		<div class="col-md-4"></div>
		<div class="col-md-4"></div>
		</div>
		<button class="showBtn">Show more</button>
	</div>
</div>


<script type="text/javascript" src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<script
  src="https://code.jquery.com/jquery-3.1.1.js"
  integrity="sha256-16cdPddA6VdVInumRGo6IbivbERE8p7CQR3HzTBuELA="
  crossorigin="anonymous"></script>

 <script type="text/javascript" src="app.js"></script>
 </body>
</html>


*{
	padding: 0px;
	margin: 0px;
	box-sizing: border-box;
}

html, body{
	padding: 0px;
	margin: 0px;
}

.container-fuid{
	min-width: 100%;

}

.col-md-4{
	width: 100%;
	height: 250px;
	background-color: gray;
	border: 1px solid black;
	  -webkit-transition: all 0.5s ease-in-out;
  -moz-transition:all 0.5s ease-in-out;
  -o-transition:all 0.5s ease-in-out;
  transition:all 0.5s ease-in-out;
}

.collapse-content{
height: 0px;
display: none;
 -webkit-transition:height 0.75s ease;
 -moz-transition:height 0.75s ease;
 -o-transition:height 0.75s ease;
 transition:height 0.75s ease;
}

.active-collapse{
  -webkit-transition:height 0.75s ease;
  -moz-transition:height 0.75s ease;
  -o-transition:height 0.75s ease;
  transition:height 0.75s ease;
height: auto;
display: inherit;
}

.showBtn{
	width: 100%;
	height: 55px;
	font-size: 19px;
	background-color: deepskyblue;
	border: none;
}