Add formula for yubikey-personalization.

Motivation for this pull request is that this library is needed to use yubikeys as a Google Authenticator replacement.

```
> brew audit yubikey-personalization
> otool -L `which ykchalresp`
/usr/local/bin/ykchalresp:
	/usr/local/Cellar/yubikey-personalization/1.12.0/lib/libykpers-1.1.dylib (compatibility version 14.0.0, current version 14.0.0)
	/usr/local/lib/libyubikey.0.dylib (compatibility version 2.0.0, current version 2.3.0)
	/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation (compatibility version 150.0.0, current version 550.44.0)
	/System/Library/Frameworks/IOKit.framework/Versions/A/IOKit (compatibility version 1.0.0, current version 275.0.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 125.2.11)
```

Name matches the [debian package](http://packages.debian.org/squeeze/yubikey-personalization).