A simple check to kill the "`" check endless loop

This patch simply checks for remaining "`" char in the "text" variable. If there are none, then the inner conditional that looks for a match is skipped. This prevents the conditional from being entered in cases where an endless loop could occur.

It makes the code below succeed where it would otherwise fail.
```javascript
Markdown("##Usage\n###Simple, `standard, awesome\n~~~\njQuery('some_selector').meltdown();\n~~~\n");
```