GitLab

Switched exception constants to const char * const (from const std::string) so we don't have to construct them all in every translation unit, and switched the exception class to derive from std::runtime_error (so it handles what() for us)

Added Anchor() regex (so that we're not just using Alphanumeric to match anchors), but it's still not 100% right (it shouldn't allow non-printable characters, e.g.). Also fixed a test that was broken along these lines (if a colon immediately follows an anchor, it's part of the anchor)

Moved all the includes to a subfolder yaml-cpp so they don't interfere with other libraries' includes

Refactored emitter operator << overloads to not template them, so it's easier to overload for pointer types

Refactored the traits a bit, and added displaying the key to string and numeric key not found errors