Release 0.0.4

[mattbennett]

• Makes use of Raven's contexts when reporting to sentry. Now populates:
  • HTTP context with the request details, if using the @http entrypoint
  • User context if any keys in nameko's context_data seem to identify a user
  • Tags context for call IDs, service and method names
  • Extra context for everything else in nameko's context_data
• Degrades nicely when the config file doesn't contain a SENTRY section at all