Try to fix travis

Author: Cat-Ion

.travis.yml

@@ -12,20 +12,23 @@ matrix:
           sources:
             - ubuntu-toolchain-r-test
           packages:
-            - g++-5
+            - g++-8
             - libunittest++-dev
       env:
-        - MATRIX_EVAL="CC=gcc-5 && CXX=g++-5"
+        - MATRIX_EVAL="CC=gcc-8 && CXX=g++-8"
       after_success:
         - make coverage
-        - coveralls 
+        - coveralls --gcov /usr/bin/gcov-8.1.0
     - os: linux
       addons:
         apt:
           sources:
             - ubuntu-toolchain-r-test
+            - llvm-toolchain-trusty-6.0
+            - sourceline: 'deb http://apt.llvm.org/trusty/ llvm-toolchain-trusty-6.0 main'
+              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
           packages:
-            - g++-5
+            - clang-6.0
             - libunittest++-dev
       env:
         - MATRIX_EVAL="CC=clang && CXX=clang++"