Log errors from gistie's xhr exchange

Previously would only show errors with HTTP 2xx responses
Update PBWebHistoryController for GTConfiguration
Update gisting to the v3 API

v1 & v2 have been dead for quite a while
Use the Personal API Access Token when posting gists

Can be created at https://github.com/settings/applications, then set with "git config --global github.token bef91b559df0014f71c212fc44171b5bc6de12e9a"
Merge branch 'refs/heads/master' into issues/203
Add pull request #203 to the change log
Merge branch 'issues/203'