Set the default operator >> to not compile unless there is a scalar conversion, so it doesn't interfere with user-defined types
Switched the utf bom checking to putback in the stream (instead of keeping a secondary buffer), which fixes a bug when there's only one ascii character
Split the yaml.h file into new/old API, which we'll then copy to yaml.h at build time (so the right one gets installed)
Set the default build to the old API, and removed the duplicate spec test implementation for the old api