fails:YAML.load returns a document from current io stream when io provided
fails:YAML.load loads strings
fails:YAML.load fails on invalid keys
fails:YAML.load accepts symbols
fails:YAML.load accepts numbers
fails:YAML.load accepts collections
fails:YAML.load parses start markers
fails:YAML.load works with block sequence shortcuts
fails:YAML.load works on complex keys
fails:YAML.load loads a symbol key that contains spaces
fails:YAML.load with iso8601 timestamp computes the microseconds
fails:YAML.load with iso8601 timestamp rounds values smaller than 1 usec to 0 
