Logstash formatter and sourcefile hook

[alxdm]

Hi,

This pull request contains two features:

1. Source File Hook which add source file and line number to entries (log output) for predefined log levels.
2. Logstash Formatter which write output log as Logstash Event (http://logstash.net/).

Thanks,
Alex Demidov

[sirupsen]

Please split your PR into two. There's already a patch like sourcefile that has not been merged yet, so it won't be accepted (perhaps you can pitch in on the other ticket? #75).

However, the Logstash formatter I'll happily accept.

[alxdm]

@sirupsen I close this pull request and will split it into two. Thanks.