added arrwo to lecture page link "Zur Veranstaltungsseite", closes #124

templates/lecture.html

@@ -25,7 +25,7 @@
 	<div class="panel-body">
 		<div class="row" style="padding: 0px;">
 			<div class="col-xs-12" style="padding-bottom: 5px;">
-				<a href="{{url_for('course', handle=course.handle)}}#lecture-{{lecture.id}}" class="btn btn-default" >Zur Veranstaltungsseite</a>
+				<a href="{{url_for('course', handle=course.handle)}}#lecture-{{lecture.id}}" class="btn btn-default" ><span class="fa fa-chevron-circle-left" aria-hidden="true"></span> Zur Veranstaltungsseite</a>
 				<ul class="list-inline pull-right">
 					<li>{{ video_embed_btn(lecture.id, course=course.handle) }}</li>
 					<li class="dropdown">{{ video_download_btn(videos) }}</li>