This patch adds support for a new Cmake option,
VALIJSON_USE_EXCEPTIONS. If specified and set to `0`, Valijson will
disable all exception throwing, add the `-fno-exceptions` compiler flag,
and print to std::err and abort where exceptions would have been thrown.
NOTE: to set the value of a CMake option, the easiest way is to modify
the appropriate source line in the <build folder>/CMakeCache.txt file.
Bug: #106
This commit contains the third major design of a C++ library for JSON Schema validation.
It is definitely not what I would consider production-ready, but I do think that the overall design of the library is robust.
