Fix an infinite loop/DoS vuln in the link rule

Makes the same modification from marked in this commit:
markedjs/marked@d53f206

Fixes issue #29

Test plan:
Run the following in node, and get output instantly:

```
require('./simple-markdown.js').defaultHtmlOutput(require('./simple-markdown.js').defaultBlockParse('[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n[+test)[]\n'));
```

package.json

@@ -1,6 +1,6 @@
 {
   "name": "simple-markdown",
-  "version": "0.2.1",
+  "version": "0.2.2",
   "description": "Javascript markdown parsing, made simple",
   "main": "simple-markdown.js",
   "scripts": {

simple-markdown.js

@@ -517,7 +517,7 @@ var TABLES = (function() {
     };
 })();
 
-var LINK_INSIDE = "(?:\\[[^\\]]*\\]|[^\\]]|\\](?=[^\\[]*\\]))*";
+var LINK_INSIDE = "(?:\\[[^\\]]*\\]|[^\\[\\]]|\\](?=[^\\[]*\\]))*";
 var LINK_HREF_AND_TITLE =
         "\\s*<?((?:[^\\s\\\\]|\\\\.)*?)>?(?:\\s+['\"]([\\s\\S]*?)['\"])?\\s*";
 var AUTOLINK_MAILTO_CHECK_R = /mailto:/i;