Avoid temporary allocations

[davidfowl]

The message parsing is all string based. While this is convenient it allocates strings to parse the redis command which is then turned into the resulting object. It would be better to parse the ReadOnlySequence directly in each of the result processors.

[thomhurst]

@davidfowl I've changed it to only allocate a string if I'm going to use it for returning etc. Is this what you mean?