Issue/1867 attach user details to a helpshift request

Adds user details to Helpshift via meta data.  This pull also populates the username and password fields of the conversation window if it can.

I'm open to ideas for how to best format the data.  

![85 automattic - helpshift](https://cloud.githubusercontent.com/assets/1220715/3649014/b8422dfa-110e-11e4-89f9-852e0f823201.jpg)