Combined the myriad ScannerExceptions and ParserExceptions to a single ParserException class that has a message and a line/column position in the file where the error occurred.
Fixed a bug in the last newline of a block folded scalar.
Specialized the overloaded [] operator for int/unsigned, and added a size() function, so that you can iterate through a sequence node like a vector.
Fixed a silly bug in the simple key pushing (queues are FIFO!).