travis: add cppcheck
Merge pull request #191 from toxeus/cppcheck

travis: add cppcheck
Added otextensions - Move OTSocket (ZMQ) out of otlib
Add otextensions to packaging
otextension: Install headerfile
Merge pull request #190 from lclc/otextensions

otextensions added - Move OTSocket / ZMQ in new lib
Fix up otextensions Makefile mods.