Added Haddock documentation for rate units.

[mtesseract]

Clearly state units for oneMinuteRate, fiveMinuteRate, fifteenMinuteRate and meanRate.
This should take care of #8

[mtesseract]

Hi, any concerns about this PR?

[iand675]

Hi, sorry for the delay in responding. The meanRate value was in fact an bug arising from doing integer division rather than floating point division. It should be in seconds. I've also updated the moving average values to operate in seconds as well, as it the way it was reporting over 5 second intervals arose from a misunderstanding when I ported this library from the Java equivalent.

I will happily accept additional documentation, but it will need to be updated to reflect these changes.

[mtesseract]

Hi Ian,

I've added two comments to your commit — looks like some testing code slipped in?

As I understand it, this commit breaks the semantics of the API. So it should include a major version bump.

Of course we can close this PR, as it's not applicable anymore.

Thanks,
Moritz