Add test for HWM behaviour for mandatory ROUTER sockets over tcp
Merge pull request #1154 from mrvn/pull-test_router_mandatory_hwm

Add test for HWM behaviour for mandatory ROUTER sockets over tcp
Document altered HWM behaviour when ZMQ_ROUTER_MANDATORY is set.
Merge pull request #1155 from mrvn/pull-document_hwm_behaviour_with_ZMQ_ROUTER_MANDATORY

Document altered HWM behaviour when ZMQ_ROUTER_MANDATORY is set.
do not silently drop messages in publisher if hwm is reached
better naming of flags and variables to real functionality: nodrop
Merge pull request #1156 from kreuzberger/master

Provide socket option for pub sockets to not silently drop message
Code cleanup
Return -1 when failed to publish message
Merge pull request #1158 from hurtonm/master

Code cleanup
Note that ZMQ_TCP_ACCEPT_FILTER is deprecated
Added AppDynamics as corporate author
Problem: ZMQ_CURVE_SECRETKEY reads beyond end of Z85 data

Solution: change setsockopts on printable keys to expect 41, nor 40
bytes. Code still accepts 40 bytes for compatibility, and copies the
key to a well-terminated string before using it.

Fixes #1148
Reworking Travis script
Minor changes to Travis CI script
Cleaned up test_xpub_nodrop

Renamed test case to actually explain what it's testing, and cleaned up
the code a little.
Merge pull request #1151 from hintjens/master

Documentation patches
Bugfix wrong CMakeLists.txt after rename of file
Merge pull request #1159 from kreuzberger/master

Bugfix wrong CMakeLists.txt after rename of file
Reset metadata for outbound messages