Add support for WhatFailureGroupHandler (Monolog ~1.11)

[mpdude]

Please tag a new version after merging this :-).

Here is an example configuration that can be used to send messages into a Logstash socket.
That socket might not exist or be not writeable in case Logstash crashes/does not run,
but you don't want that to affect your application.

monolog:
  handlers:

    ignore_failures:
      type: whatfailuregroup
      members: [ main ]

    main:
      type:  socket
      connection_string: unix:///path/to/logstash/socket
      level: debug
      connection_timeout: 0.05

[mpdude]

The Travis failure is due to some XML import problems in HHVM. fabpot complains about CS in places not touched by this PR.

Please merge.

[mpdude]

bump

[nicolas-grekas]

can you please rebase on 2.7?

[mpdude]

2.7?

[Seldaek]

Thanks

[stof]

@nicolas-grekas there is no 2.7 branch in the bundle (the bundle has its own release cycle)