Merge pull request #1 from hintjens/master

Draft of protocol codec
libzyre not used in libxrap
Merge pull request #2 from toanju/master

libzyre not used in libxrap
Skeleton client/server test
Fix crash in _dup method
Updated man page
Switched to using zeromq/zproto

- also changed content-type to longstr
Rebuilt codec
Merged /model into /src