fix xibbling plugins without blocks

* Fix rule processing in code @jHoldroyd
* Add example
* Rewrite tests from ECMA2017 to ECMA 5

Author: Pasha Rumkin

lib/marked.js

@@ -201,7 +201,7 @@ Lexer.prototype.token = function(src, top, bq) {
         type: 'plugin',
         plugin: cap[1],
         params: cap[3],
-        block: cap[4].replace(new RegExp('^' + cap[4].match(/^\s+/)[0], 'gm'), ''),
+        block: cap[4] !== undefined ? cap[4].replace(new RegExp('^' + cap[4].match(/^\s+/)[0], 'gm'), '') : undefined,
       });
       continue;
     }

test/index.js

@@ -87,7 +87,12 @@ function runTests(engine, options) {
   var renderer = new marked.Renderer();
   renderer.plugins = {};
   renderer.plugins.github = function(params, body) {
-    return `<a href="https://github.com/${body}">${body}</a>`;
+    return '<a href="https://github.com/' + body + '">' + body + '</a>';
+  };
+  
+  renderer.plugins.link = function(params, body) {
+    var parts = params.split(/\s*,\s*/);
+    return '<a href="' + parts[1] + '">' + parts[0] + '</a>';
   };
 
 main:

test/tests/plugin_github.html

@@ -1 +1,2 @@
+<a href="https://github.com">github</a>
 <a href="https://github.com/chjj/marked">chjj/marked</a>

test/tests/plugin_github.text

@@ -1,3 +1,4 @@
+@link(github, https://github.com)
 @github(https)
   chjj/marked