Merge pull request RestComm#146 from StephenDwyer-kcom/master

…ing as expected

…r class; changes require around peer selection and should move away from using CC-Request-Number AVP for signifying resubmissions. Interim commit only to manage change

…iting behaviour in WeightedRoundRobinRouter class. Tests added to validate WeightedRoundRobinResubmittingRouter selects previously unattempted peers for a resubmission of an existing message, based on existing weighted round robin algorithm.

…tting requests which have received a Busy or Unable to Deliver Answer from one peer, to an alternative peer, and to avoid perpetual re-submission of such requests

This reverts commit 2575d51.