add @supports support

Author: tj

index.js

@@ -113,6 +113,20 @@ Compiler.prototype.charset = function(node){
   return '@charset ' + node.charset + ';\n';
 };
 
+/**
+ * Visit supports node.
+ */
+
+Compiler.prototype.supports = function(node){
+  return '@supports '
+    + node.supports
+    + ' {\n'
+    + this.indent(1)
+    + node.rules.map(this.visit, this).join('\n\n')
+    + this.indent(-1)
+    + '\n}';
+};
+
 /**
  * Visit keyframes node.
  */

test/cases/supports.css

@@ -0,0 +1,10 @@
+
+@supports (display: flex) {
+  div {
+    display: flex;
+  }
+
+  div {
+    something: else;
+  }
+}