Merge pull request #5 from nicolaje/master

Travis-ci integration + minimalist C++ client-api
Added "clear" action (clears the contents of a figure) to the VIBes server.
Merge pull request #6 from nicolaje/master

Changed the C++ client-api to open the file in "append" mode, corrected ...
Changed the way relative path is set for C++ examples CMakeLists.txt file
This commit fixes #7, adds a sivia-simple example (with Luc Jaulin interval library) and fixes some minor issues with the vibes C++ API
Introduce a PONG example with the C++ API