Added a .travis.yml

It builds on Ubuntu 14.04 with gcc-4.9, gcc-5, clang-3.6, 3.7 and 3.8.
It uses the boost, OpenCV and Eigen from the system (apt-get install).

.travis.yml

@@ -0,0 +1,30 @@
+sudo: required
+dist: trusty
+
+language: cpp
+
+env:
+  - C_COMPILER=gcc-4.9 CXX_COMPILER=g++-4.9
+  - C_COMPILER=gcc-5 CXX_COMPILER=g++-5
+  - C_COMPILER=clang-3.8 CXX_COMPILER=clang++-3.8
+  - C_COMPILER=clang-3.6 CXX_COMPILER=clang++-3.6
+  - C_COMPILER=clang-3.7 CXX_COMPILER=clang++-3.7
+
+before_install:
+  - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
+  - wget -O - http://llvm.org/apt/llvm-snapshot.gpg.key | sudo apt-key add -
+  - echo "deb http://llvm.org/apt/trusty/ llvm-toolchain-trusty main" | sudo tee -a /etc/apt/sources.list
+  - echo "deb http://llvm.org/apt/trusty/ llvm-toolchain-trusty-3.6 main" | sudo tee -a /etc/apt/sources.list
+  - echo "deb http://llvm.org/apt/trusty/ llvm-toolchain-trusty-3.7 main" | sudo tee -a /etc/apt/sources.list
+  - sudo apt-get update -q
+  - sudo apt-get install gcc-4.9 g++-4.9 gcc-5 g++-5 -y
+  - sudo apt-get install clang-3.6 clang-3.7 clang-3.8 -y
+  - sudo apt-get install libboost-all-dev libeigen3-dev libopencv-dev opencv-data -y
+
+before_script:
+  - mkdir build
+  - cd build
+  - cmake -DOpenCV_haarcascades_DIR=/usr/share/opencv/haarcascades/ -DCMAKE_C_COMPILER=${C_COMPILER} -DCMAKE_CXX_COMPILER=${CXX_COMPILER} ..
+
+script:
+  - make VERBOSE=1