better layout on md devices

approot/explore.xml

@@ -3,10 +3,10 @@
 
 <message id="Lms.Explore.template">
 	<div class="row">
-		<div class="col-lg-8">
+		<div class="col-md-8">
 			${contents class="Lms-explore-contents"}
 		</div>
-		<div class="col-lg-4">
+		<div class="col-md-4">
 			${filters class="well well-sm"}
 			${info class="well well-sm"}
 		</div>

approot/playhistory.xml

@@ -4,7 +4,7 @@
 
 <message id="Lms.PlayHistory.template">
 	<div class="row">
-		<div class="col-lg-8">
+		<div class="col-md-8">
 			<div class="page-header">
 				<h2>${tr:Lms.PlayHistory.playhistory}</h2>
 			</div>

approot/playqueue.xml

@@ -9,7 +9,7 @@
 
 <message id="Lms.PlayQueue.template">
 	<div class="row">
-		<div class="col-lg-8">
+		<div class="col-md-8">
 			<div class="page-header">
 				<h2>${tr:Lms.PlayQueue.playqueue}</h2>
 				${clear-btn}${shuffle-btn}${repeat-btn}${radio-btn}