* - allow defining a specific path to Cairo libraries and headers
- link against Xau library if needed
* changes in response to review
* removed the libXau bit as it is not needed
* New syntax to import Qt5 dependency in MolDraw2D
* In QTDemo, not necessary to import Qt explicitly because it is automatically imported through target MolDraw2D
* improve import of Cairo dependency
* Remove explicit linking of Cairo in C++ examples
* Use imported targets for Boost
* Using imported CMake targets for Eigen
* Use imported targets for Threads
* Simplify sample CMakeLists
* Remove duplication
* a couple small changes for travis
* typo
* update toolchain to trusty
* switch to requiring at least boost 1.56
* typo
* update boost dependency to pull in the build that has more libraries
* meaningless commit to trigger travis
* switch to ust libc++
* install libc++
* check abi
* try the other one; disable py27 for the moment to speed things up
* switch to c++11, that seems necessary with the conda boost builds at the moment
* re-enable python2.7
