Changes in version 0.3.1 (10 April 2015)

* implemented asynchronous queries, bound to Context()
  objects, and introduced Context.run() method.  See
  getdns.readthedocs.org

* queries now return a Result() object, with attributes.
  See getdns.readthedocs.org

* removed leading GETDNS_ in all constants
  (i.e. getdns.GETDNS_RRTYPE_AAAA is now getdns.RRTYPE_AAAA)

* added getdns.get_errorstr_by_id() method, making it easier
  to provide user-friendly error messages

* prettied up printing of canonical names in Result object

* str and repr printing has been added to both Context and
  Result objects

* dead code removed

* replaced instances of getdns_strerror() with
  getdns_get_errorstr_by_id()

* fixed incorrect error return from Result construction

* moved __version__ attribute from Context to top-level
  getdns module

* made exception handling within the module more consistent

* added documentation describing getdns.error

* broke out query types
