Here's a link: https://news.ycombinator.com/item?id=7265814
There are also two recent blog posts we've made which might be helpful. The first is about the funding, and second is our 2013 Year-In-Review, which highlights what we've been working on.
https://zenpayroll.com/blog/series-a-funding https://zenpayroll.com/blog/zenpayroll-2013-year-in-review
Hope this helps!