remove redundant Travis CI

.travis.yml

@@ -1,27 +0,0 @@
-language: cpp
-os: linux
-compiler:
-  - gcc
-  - clang
-
-before_install:
-  - test -n $CC && unset CC
-
-addons:
-  apt:
-    sources:
-      - ubuntu-toolchain-r-test
-    packages:
-      - libgomp1
-      # - gcc-6
-
-script:
-  - export OMP_NUM_THREADS=2
-  - export LD_LIBRARY_PATH=$(if [[ $CXX == "clang++" ]]; then echo -n '/usr/local/clang/lib'; fi)
-  - mkdir build
-  - cd build
-  - cmake .. -DUSE_OPENMP=OFF
-  - make
-  - rm -rf *
-  - cmake .. -DUSE_OPENMP=ON
-  - make