Travis-CI: add packages for the various clang versions

I tried to set up the matrix for various clang. I had trouble with:
 - linux + clang-3.5 (libstdc++ didnt work with this version and I couldnt figure out how to get it to use libc++)
 - linux + clang-3.8 (appears that this isnt ready yet)
 - linux + gcc-5 (the tool "gcc-5" wasnt found)

Anyway, the matrix seems to work in these configs at least.

Hint: it's the red pill.

Author: jaredgrubb

.travis.yml

@@ -1,13 +1,54 @@
 language: cpp
-
 sudo: false   # Use the new container infrastructure
 
-compiler:
-  - clang
-  - gcc
+matrix:
+  include:
+    - os: linux
+      env: 
+        - COMPILER=clang++-3.6 STDLIB=libc++
+      addons:
+        apt:
+          sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-precise-3.6']
+          packages: ["clang-3.6"]
+
+    - os: linux
+      env: 
+        - COMPILER=clang++-3.7 STDLIB=libc++
+      addons:
+        apt:
+          sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-precise-3.7']
+          packages: ["clang-3.7"]
+
+    - os: osx
+      osx_image: xcode6.4
+      env: 
+        - COMPILER=clang++ V='Apple LLVM 6.4'
+        - COMPILER=clang++ V='Apple LLVM 6.4' WITH_CPP14=true
+
+    - os: osx
+      osx_image: xcode7
+      env: 
+        - COMPILER=clang++ V='Apple LLVM 7.0'
+        - COMPILER=clang++ V='Apple LLVM 7.0' WITH_CPP14=true
+
+before_install:
+  - |
+    if [[ "${TRAVIS_OS_NAME}" == "osx" ]]; then
+      brew install cmake
+    fi
+
+  - CMAKE_CXX_FLAGS+=" -Wall"
+
+  - if [[ "${WITH_CPP14}" == "true" ]]; then CMAKE_OPTIONS+=" -DWITH_CPP14=1"; fi
+  - if [[ "${STDLIB}" == "libc++" ]]; then CMAKE_CXX_FLAGS+=" -stdlib=libc++"; fi
+
+  - sh ${COMPILER} --version || true
 
 before_script:
-  - cmake -DWITH_TESTS=1 -DWITH_EXAMPLE=1 .
+  - rm -rf build/
+  - mkdir build
+  - cd build
+  - cmake -DCMAKE_CXX_COMPILER=${COMPILER} -DCMAKE_CXX_FLAGS=${CMAKE_CXX_FLAGS} -DWITH_TESTS=1 -DWITH_EXAMPLE=1 ${CMAKE_OPTIONS} ..
 
 script: 
   - cmake --build .

CMakeLists.txt

@@ -3,6 +3,8 @@ cmake_minimum_required(VERSION 2.6.4)
 option(WITH_TESTS           "Build tests."       OFF)
 option(WITH_EXAMPLE         "Build example."     OFF)
 option(WITH_STATIC          "Build static libs." ON)
+option(WITH_CPP11           "Build with C++11."  ON)
+option(WITH_CPP14           "Build with C++14."  OFF)
 
 project(docopt.cpp)
 include_directories("${PROJECT_SOURCE_DIR}")
@@ -22,7 +24,11 @@ if(WITH_STATIC)
 endif()
 add_library(docopt SHARED ${DOCOPT_SRC})
 
-add_definitions("-std=c++11")
+if(WITH_CPP14)
+    add_definitions("-std=c++14")
+elseif(WITH_CPP11)
+    add_definitions("-std=c++11")
+endif()
 
 ########################################################################
 # tests