534:debug:Regular Expression Denial of Service

[shepdelacreme]

CVES CVE-2017-16137
CWE CWE-400
References: - Issue #501

• PR #504
  Affected versions of debug are vulnerable to regular expression denial of service when untrusted user input is passed into the o formatter.

As it takes 50,000 characters to block the event loop for 2 seconds, this issue is a low severity issue.
@marshyski @defionscode