* Update dependency on libexpat to version 2.2.5
This new version of the conan recipe contain packages for new compilers
* Get gtest and libcurl from bincrafters
* Update the zlib dependency
* Use clang-5.0
- Specify concrete ubuntu and mac versions
- Use latest conan version
- Fix the profiles for linux and mac
- Use new version of expat (avilable in conan-center)
- Install urllib3 as suggested in python guidelines
- Use virtualenv with python3