Fix incorrect parameters to Trace::TraceId.new

 - broken by commit 22a12cff2214e39fe948bd2c1b4a4790e0b5987c
 - also remove extra commas in header names
 - add parsing of flags from header

Signed-off-by: Jeff Smick <jeff@twitter.com>
Allow config hash to be passed on initialization

 - app.config is not always valid except for Rails 3+

Signed-off-by: Jeff Smick <jeff@twitter.com>
sync oss