Made library easier to use from a CMake project: simply add_subdirectory(ArduinoJson/src)

.travis.yml

@@ -5,6 +5,9 @@ compiler:
   - clang
 before_install:
   - pip install --user cpp-coveralls
+  - mkdir -p /tmp/cmake
+  - curl https://cmake.org/files/v3.4/cmake-3.4.0-Linux-x86_64.tar.gz | tar xz -C /tmp/cmake --strip 1
+  - export PATH=/tmp/cmake/bin:$PATH
   - "/sbin/start-stop-daemon --start --quiet --pidfile /tmp/custom_xvfb_1.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :1 -ac -screen 0 1280x1024x16"
   - sleep 3
   - export DISPLAY=:1.0