Contributors associated with pledges have a state: they can be confirmed or unconfirmed. They also have some important meta data, namely when they were confirmed. Thus, managing contributor data for pledges is more robust if we treat them as their own post type instead of as a multidimensional array of post meta data.
This also reorganizes some of the functions related to pledges so that things are more consistent between the pledge CPT and the contributior CPT.
Fixes#11
This starts to address several items in the roadmap, but probably doesn't fully address any of them. It takes the plugin code that was written several months ago, before the scope of this project was fully sorted out, and refactors it to be a starting point for the roadmap.
* Adds template files for form inputs that can be used to both create new pledges and manage existing pledges
* Does some validation and sanitization work on form submissions
* Adds a custom post status for deactivated pledges
