generated donation, interest, & transaction

the donation process. a donation is created by a donor (or user that's not logged in) and recipients can show interest. A coordinator will create a transaction between a donation and a recipient. basic views and forms.

issue #8 
Postgres supports arrays as a datatype, so we can do something like this? http://rny.io/rails/postgresql/2013/07/28/tagging-in-rails-4-using-postgresql-arrays.html