Ensure BYEs work through proxies
Add [routes] to every message
Put [routes] at the end of the headers to avoid issues with old versions of SIPp

@see http://www.mail-archive.com/sipp-users@lists.sourceforge.net/msg01114.html
Explicitly set From for BYEs
Make specified From consistent
Make specified Contact consistent
Merge pull request #14 from sfgeorge/feature/various-tweaks

Various tweaks