ZConfig logging support for raven

This package allows enabling raven, the Python interfacet to Sentry via a ZConfig logging configuration like:

<logger>
  %import j1m.ravenzconfig
  <sentry>
    dsn https://abc:def@example.com/42
  </sentry>
</logger>

Additional options are supported, including logging level and options accepted by the raven client. See the raven client documentation.

Here's an example that uses all of the options:

<logger>
   %import j1m.ravenzconfig
   <sentry>
     level WARNING
     dsn https://abc:def@example.com/42
     site test-site
     name test
     release 42.0
     environment testing
     exclude_paths /a /b
     include_paths /c /d
     sample_rate 0.5
     list_max_length 9
     string_max_length 99
     auto_log_stacks true
     processors x y z
   </sentry>
 </logger>

The defaults for level and sample_rate are ERROR and 1.0. For other options, other than the required dsn, the defaults are unset.