1.24.0

• BC Notice: If you are extending any of the Monolog's Formatters' normalize method, make sure you add the new $depth = 0 argument to your function signature to avoid strict PHP warnings. See #808 for more details.
• Added a ResettableInterface in order to reset/reset/clear/flush handlers and processors
• Added a ProcessorInterface as an optional way to label a class as being a processor (mostly useful for autowiring dependency containers)
• Added a way to log signals being received using Monolog\SignalHandler
• Added ability to customize error handling at the Logger level using Logger::setExceptionHandler
• Added InsightOpsHandler to migrate users of the LogEntriesHandler
• Added protection to NormalizerFormatter against circular and very deep structures, it now stops normalizing at a depth of 9
• Added capture of stack traces to ErrorHandler when logging PHP errors
• Added RavenHandler support for a contexts context or extra key to forward that to Sentry's contexts
• Added forwarding of context info to FluentdFormatter
• Added SocketHandler::setChunkSize to override the default chunk size in case you must send large log lines to rsyslog for example
• Added ability to extend/override BrowserConsoleHandler
• Added SlackWebhookHandler::getWebhookUrl and SlackHandler::getToken to enable class extensibility
• Added SwiftMailerHandler::getSubjectFormatter to enable class extensibility
• Dropped official support for HHVM in test builds
• Fixed normalization of exception traces when call_user_func is used to avoid serializing objects and the data they contain
• Fixed naming of fields in Slack handler, all field names are now capitalized in all cases
• Fixed HipChatHandler bug where slack dropped messages randomly
• Fixed normalization of objects in Slack handlers
• Fixed support for PHP7's Throwable in NewRelicHandler
• Fixed race bug when StreamHandler sometimes incorrectly reported it failed to create a directory
• Fixed table row styling issues in HtmlFormatter
• Fixed RavenHandler dropping the message when logging exception
• Fixed WhatFailureGroupHandler skipping processors when using handleBatch
  and implement it where possible
• Fixed display of anonymous class names