Merge pull request #1 from hintjens/master

Starting on drops prototype
Merge pull request #2 from hintjens/master

Fixed build, project is still empty
Merge pull request #3 from hintjens/master

Added Travis CI script
Merge pull request #4 from hintjens/master

Still does nothing, now uses two threads to do it
Fixed doc/Makefile.am -- via CZMQ