Problem: current libzmq is not tested

Solution: update default libzmq version to 4.3.1, and add explicit test for 4.2.5, update README accordingly

.travis.yml

@@ -42,6 +42,10 @@ matrix:
     - os: linux
       env: ZMQ_VERSION=4.2.0 BUILD_TYPE=pkgconfig
 
+    # GCC default, draft disabled, latest 4.2.x libzmq (defined in ci_build.sh)
+    - os: linux
+      env: ZMQ_VERSION=4.2.5
+
     # GCC default, draft disabled, default libzmq (defined in ci_build.sh)
     - os: linux
 

README.md

@@ -23,9 +23,10 @@ Supported platforms
 ===================
 
  - Only a subset of the platforms that are supported by libzmq itself are supported. Some features already require a compiler supporting C++11. In the future, probably all features will require C++11. To build and run the tests, CMake and Catch are required.
- - Tested libzmq versions are
+ - Any libzmq 4.x version is expected to work. DRAFT features may only work for the most recent tested version. Currently explicitly tested libzmq versions are
    - 4.2.0 (without DRAFT API)
-   - 4.2.5 (with and without DRAFT API)
+   - 4.2.5 (without DRAFT API)
+   - 4.3.1 (with and without DRAFT API)
  - Platforms with full support (i.e. CI executing build and tests)
    - Ubuntu 14.04 x64 (with gcc 4.8.4) (without DRAFT API only)
    - Ubuntu 14.04 x64 (with gcc 7.3.0)

ci_build.sh

@@ -4,7 +4,7 @@ set -x
 set -e
 
 BUILD_TYPE=${BUILD_TYPE:-cmake}
-ZMQ_VERSION=${ZMQ_VERSION:-4.2.5}
+ZMQ_VERSION=${ZMQ_VERSION:-4.3.1}
 ENABLE_DRAFTS=${ENABLE_DRAFTS:-OFF}
 COVERAGE=${COVERAGE:-OFF}
 LIBZMQ=${PWD}/libzmq-build