Merge pull request #609 from ckamm/tests

Make pipeline/reqrep tests try tcp:// endpoints.
Got new test cases working with libzmq

* disabled the specific tests that do not work (yet) on libzmq
* cleaned up one source (test_spec_rep.c) but the others need similar work
* added sleep in test_spec_rep to allow connects time to happen; this would
  not be needed if we connected out to the REP peers instead in from them,
  but I didn't want to change the logic of the test code.
Merge pull request #610 from hintjens/master

Problem: new spec test cases don't all work
update to include stream.cpp and curve related
Merge pull request #611 from pijyoi/master

update Makefile to include new files
Converted README to markdown + added travis build img
Merge pull request #612 from ulikoehler/markdown

Converted README to markdown
REQ sockets drop replies from unasked peers.

* Add lb_t::sendpipe() that returns the pipe that was used for sending,
  similar to fq_t::recvpipe().
* Add forwarder functions to dealer_t to access these two.
* Add logic to req_t to ignore replies on pipes that are not the one
  where the request was sent.
* Enable test in test_spec_req.