Adding Timestamps and minor refactor

[Tuxino]

Hi Marco

Another pull request related to the following issue #7

Timestamps added to all collectors
Some refactoring of tests / exposers
readme updated

Signed-off-by: David Aspden [email protected]

[marcobreveglieri]

Hi Tuxino,
I peeked at the changes proposed in the pull request.

There are many interventions on different points, even structural ones, like a new private TLock object in descendant classes of collectors, just to name one.

I wanted to ask you if these improvements are related to effective problems that emerged from tests and usages that you have made in production: since these are fairly internal changes to classes that are fundamental for the library, and since I have not received any feedback on troubles with them till now, I want to be sure not to introduce regression errors within the library.

Can you give me some brief details about this?

Thanks as always for your collaboration! 🤗

Regards,
Marco.