Fix for salts replace

The regex replace for keys + salts in wp-config was failing in some instances (notably when working with certain existing wp-configs).

![screen shot 2013-10-22 at 10 45 51 am](https://f.cloud.github.com/assets/84145/1382728/3f44913e-3b32-11e3-8a7a-14e28b9f6a76.png)

This *should* match everything from `/**#@+...*/` and `/**#@-*/`, and replace everything between them. (We should test the heck out of this before merging).