ADD PD1 Segment.

The PD1 (patient demographic information) segment allows us
to send information about the primary care provider (us) to our
vendors, mainly this is used to send our practice NPI number.

We could also, you know, send patient demographics not included
with the other three segments devoted to patient demographics.

http://jwenet.net/notebook/1777/1280.html
Merge pull request #5 from IoraHealth/pr-add_pd1_segment

ADD PD1 Segment.