2 New Merge Fields types, 4 New STS Stats calls

[jesse p]

With our release this week there were a few API changes/updates that
rolled out.

First, as mentioned on our main blog, there are now "birthday" and
"zip" merge field types:

http://blog.mailchimp.com/zip-field-for-signup-forms/
http://blog.mailchimp.com/new-birthday-field-for-signup-forms/

Those are both available for use in all of the listMergeVar* methods
and can, of course, be set via listSubscribe() and
listBatchSubscribe(). They are also supported for segmentation, though
given its use case, "zip" types have a limited number of valid
operations as documented here:

http://apidocs.mailchimp.com/rtfm/campaignsegmenttest.func.php


Additionally, there are now four new STS Stat related calls available.
The purpose of all of them is to expose all of the extra tracking data
for clicks/opens/etc we are collecting for your account. They are:

* GetTags
* GetSendStats
* GetUrls
* GetUrlStats

Full documentation on them can be found here:

http://apidocs.mailchimp.com/sts/1.0/#mcstats