v4.1.0

• Added support for collecting system and process metrics (#361)
• Added an OpenTracing bridge (#388)
• Added transaction.sampled to errors (#371)
• Added transaction.type to errors (#391)
• Added parsing of /proc/self/cgroup to capture container meta data (#352)
• Added option to configure logging for Flask using a log level (#344)
• Added capture_headers config option (#392)