Merge branch 'travis_update'

Use new xcode and GCC 7

.travis.yml

@@ -1,15 +1,17 @@
 language: generic
 sudo: false
 os: osx
-env: CF=
+env:
+  global:
+    - CF=-DCOMPILE_OFFLINE_TESTS=1
 
 matrix:
   include:
 #    - osx_image: xcode7.3 #default
 #      before_install: &brew
 #      - brew update
 #      - brew install hidapi
-    - osx_image: xcode6.4
+    - osx_image: xcode9.1
     - osx_image: xcode8.2
     - os: linux
       dist: trusty
@@ -32,6 +34,16 @@ matrix:
             - libhidapi-dev
             - g++-6
           sources: *sources
+    - os: linux
+      dist: trusty
+      env: COMPILER_NAME=gcc CXX=g++-7 CC=gcc-7
+      addons:
+        apt:
+          packages:
+            - cmake
+            - libhidapi-dev
+            - g++-7
+          sources: *sources
     - os: linux
       dist: trusty
       env: COMPILER_NAME=clang CXX=clang++-3.8 CC=clang-3.8
@@ -55,4 +67,5 @@ install:
 
 script:
   - make -j2
-  - ctest -VV
+  - ctest -VV
+  - mkdir install && make install DESTDIR=install