avoid unneeded whitespace in style XML output

lib/carto/tree/style.js

@@ -28,19 +28,19 @@ tree.StyleXML = function(name, attachment, definitions, env) {
     if (image_filters.length) {
         attrs_xml += ' image-filters="' + image_filters.map(function(f) {
             return f.ev(env).toXML(env, true, ',', 'image-filter');
-        }).join(',') + '" ';
+        }).join(',') + '"';
     }
 
     if (comp_op.length) {
-        attrs_xml += ' comp-op="' + comp_op[0].value.ev(env).toString() + '" ';
+        attrs_xml += ' comp-op="' + comp_op[0].value.ev(env).toString() + '"';
     }
 
     if (opacity.length) {
-        attrs_xml += ' opacity="' + opacity[0].value.ev(env).toString() + '" ';
+        attrs_xml += ' opacity="' + opacity[0].value.ev(env).toString() + '"';
     }
     var rule_string = rules.join('');
     if (!attrs_xml && !rule_string) return '';
-    return '<Style name="' + name + '" filter-mode="first" ' + attrs_xml + '>\n' + rule_string + '</Style>';
+    return '<Style name="' + name + '" filter-mode="first"' + attrs_xml + '>\n' + rule_string + '</Style>';
 };
 
 })(require('../tree'));

test/rendering-mss/quoted_attr.xml

@@ -1,4 +1,4 @@
-<Style name="style-power" filter-mode="first" >
+<Style name="style-power" filter-mode="first">
   <Rule>
     <Filter>([power] = 'generator') and ([generator:source] = 'wind')</Filter>
     <MarkersSymbolizer width="0" />

test/rendering-mss/style-level-prop-only.xml

@@ -1,2 +1,2 @@
-<Style name="style" filter-mode="first"  opacity="0.5" >
+<Style name="style" filter-mode="first" opacity="0.5">
 </Style>

test/rendering-mss/style-level-prop-only2.xml

@@ -1,2 +1,2 @@
-<Style name="style" filter-mode="first"  comp-op="color-burn" >
+<Style name="style" filter-mode="first" comp-op="color-burn">
 </Style>

test/rendering-mss/style-level-prop-only3.xml

@@ -1,2 +1,2 @@
-<Style name="style" filter-mode="first"  image-filters="invert" >
+<Style name="style" filter-mode="first" image-filters="invert">
 </Style>