Various

Remaining issues uglify-js reports:

```
WARN: Side effects in initialization of unused variable check [C:\Users\xmr\Desktop\markdown-js\lib\markdown.js:1039,10]
WARN: Side effects in initialization of unused variable old_tree [C:\Users\xmr\Desktop\markdown-js\lib\markdown.js:706,10]
```

I'll leave these for @ashb @evilstreak to fix.