Merge pull request diffblue#235 from diffblue/feature/travis_build_with_j2

Introducing '-j2' option to Travis builds.

Author: marek-trtik

.travis.yml

@@ -161,7 +161,7 @@ jobs:
 install:
   - ccache --max-size=1G
   - cmake . -Bbuild "-DCMAKE_CXX_COMPILER=${COMPILER}" "-DCMAKE_BUILD_TYPE=${BUILD_TYPE}" "-Denable_security_tests=${RUN_SECURITY_TESTS}" "-Denable_cbmc_tests=${RUN_CBMC_TESTS}"
-  - ( cd build; make install )
+  - ( cd build; make install -j2 )
 
 # LOCAL CHANGES: Added cbmc/ prefix, and added unit and regression tests to the end of the list.