Check toMillis overflow in operators with Duration

[fvasco]

Fix #868

[fvasco]

Hi @qwwdfsad
I added some test, I you need some extra ones please notify me.

I have to confide you a problem, gradle test does not work on any my computers.
So I had tested all TimeTest methods manually, but unfortunately I does not know if they compile. Sorry for my miss.
Providing a battle tested docker image is a great help for me.

[fvasco]

Please wait,
I wish to add some more tests and handle sub millisecond duration for all operators.

[fvasco]

Hi @qwwdfsad
I catch this opportunity to fix another issue, any positive duration less than 1ms is truncated to 0ms, so no delay happens and withTimeout crashes.
To fix this issue all strictly positive duration are coerced in 1..Long.MAX_VALUE milliseconds.
What do you think?

[qwwdfsad]

I think this is a good idea, thank you.
I've pushed your branch, improved documentation and tests and will merge it manually as soon as tests are passed.

Thank you for your contribution!

[qwwdfsad]

Merged manually