Motivation:

During proposal review, it was pointed out that the code with a position index was redundant and error prone over relying on `ByteBuffer`'s `readerIndex`.

Modifications:

Refactored `RESPTranslator` to rely on `ByteBuffer.readerIndex` for position of current parsing cursor,
and eliminated `ParsingResult` enum to instead return `RESPValue?`.

The implementation for writing out `RESPValue` has been expanded to `RESPValueConvertible` and moved to an extension of `ByteBuffer`.

Result:

Parsing `RESPValue` into and out of `ByteBuffer` should be less error-prone and more straight forward.

This contributes to issues #47 and #55