rename top/bottom to first/last in control classes, thanks @yohanboniface

dist/leaflet.css

@@ -199,11 +199,11 @@
 	background-color: #fff;
 	border-bottom: 1px solid rgba(0,0,0,0.2);
 	}
-.leaflet-bar-part-top {
+.leaflet-bar-part-first {
 	-webkit-border-radius: 4px 4px 0 0;
 	        border-radius: 4px 4px 0 0;
 	}
-.leaflet-bar-part-bottom {
+.leaflet-bar-part-last {
 	-webkit-border-radius: 0 0 4px 4px;
 	        border-radius: 0 0 4px 4px;
 	border-bottom: none;
@@ -213,11 +213,11 @@
 	-webkit-border-radius: 10px;
 	        border-radius: 10px;
 	}
-.leaflet-touch .leaflet-bar-part-top {
+.leaflet-touch .leaflet-bar-part-first {
 	-webkit-border-radius: 7px 7px 0 0;
 	        border-radius: 7px 7px 0 0;
 	}
-.leaflet-touch .leaflet-bar-part-bottom {
+.leaflet-touch .leaflet-bar-part-last {
 	-webkit-border-radius: 0 0 7px 7px;
 	        border-radius: 0 0 7px 7px;
 	border-bottom: none;

src/control/Control.Zoom.js

@@ -18,13 +18,13 @@ L.Control.Zoom = L.Control.extend({
 		this._zoomInButton = this._createButton('+', 'Zoom in',
 		        zoomName + '-in ' +
 		        partName + ' ' +
-		        partName + '-top',
+		        partName + '-first',
 		        container, this._zoomIn,  this);
 
 		this._zoomOutButton = this._createButton('-', 'Zoom out',
 		        zoomName + '-out ' +
 		        partName + ' ' +
-		        partName + '-bottom',
+		        partName + '-last',
 		        container, this._zoomOut, this);
 
 		map.on('zoomend', this._updateDisabled, this);