travis: add msgpack

.travis.yml

+sudo: required
+
+services:
+  - docker
+
 language: cpp
 
 compiler:
@@ -13,7 +18,8 @@ addons:
 before_install:
   - echo $LANG
   - echo $LC_ALL
-  - if [ $TRAVIS_OS_NAME == osx ]; then brew update && brew install llvm36 && brew install gnutls && brew link --force llvm36; fi
+  - if [ $TRAVIS_OS_NAME == linux ]; then git clone https://github.com/msgpack/msgpack-c.git && cd msgpack-c && mkdir build && cmake .. && make -j && sudo make install; fi
+  - if [ $TRAVIS_OS_NAME == osx ]; then brew update && brew install llvm36 && brew install msgpack && brew install gnutls && brew link --force llvm36; fi
 
 before_script:
   - if [ $TRAVIS_OS_NAME == linux ]; then travis_retry ./autogen.sh && ./configure; fi