add dedicated leave button to header

src/skins/vector/css/molecules/RoomHeader.css

@@ -138,6 +138,16 @@ limitations under the License.
     visibility: visible;
 }
 
+.mx_RoomHeader_leaveButton {
+    visibility: hidden;
+    margin-top: -1px;
+}
+
+.mx_RoomHeader_wrapper:hover .mx_RoomHeader_leaveButton {
+    visibility: visible;
+}
+
+
 .mx_RoomHeader_nameEditing {
     padding-left: 8px;
     padding-right: 16px;

src/skins/vector/img/leave.svg

@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Generator: Adobe Illustrator 19.1.0, SVG Export Plug-In . SVG Version: 6.00 Build 0)  -->
+<svg version="1.1" id="Layer_1" xmlns:sketch="http://www.bohemiancoding.com/sketch/ns"
+	 xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" viewBox="-1 -1 20 26"
+	 xml:space="preserve">
+<style type="text/css">
+	.st0{fill:none;stroke:#76CFA6;}
+	.st1{fill:#76CFA6;}
+</style>
+<g id="Page-1" sketch:type="MSPage">
+	<g id="Exit-Copy-6" sketch:type="MSLayerGroup">
+		<path id="Rectangle-140_1_" sketch:type="MSShapeGroup" class="st0" d="M4.4,0.5h7.5c2.2,0,4,1.8,4,4v14c0,2.2-1.8,4-4,4H4.4
+			c-2.2,0-4-1.8-4-4v-14C0.4,2.3,2.2,0.5,4.4,0.5z"/>
+		<g id="Rectangle-140_2_">
+			<g>
+				<path class="st1" d="M12,23H4.5C2,23,0,21,0,18.5v-14C0,2,2,0,4.5,0H12c2.5,0,4.5,2,4.5,4.5v14C16.4,21,14.4,23,12,23z M4.4,1
+					C2.5,1,0.9,2.6,0.9,4.5v14c0,1.9,1.6,3.5,3.5,3.5h7.5c1.9,0,3.5-1.6,3.5-3.5v-14c0-1.9-1.6-3.5-3.5-3.5H4.4z"/>
+				<g>
+					<path class="st0" d="M3.2,20.6l8.3-1.8c1.1-0.2,2-1,2-1.7V5.7c0-0.7-0.9-1.4-2-1.7L3.2,2.2"/>
+				</g>
+			</g>
+		</g>
+		<circle id="Oval-605" sketch:type="MSShapeGroup" class="st1" cx="10.7" cy="11.1" r="1">
+		</circle>
+	</g>
+</g>
+</svg>