conversion to and from scala std duration

[wookietreiber]

• provides a solution for Compatibility with scala duration #71 based on milliseconds
• since 2.9.1 and 2.9.2 do not contain the std duration implementation,
  these would need to be dropped (is it still necessary to support
  these?)
• renames DateImplicits to ConversionImplicits

[gakuzzzz]

Thanks for sending PR.

Would you tell us more detail why DateImplicits need to rename?
This change breaks compatibility.

regards,

[gakuzzzz]

We can accept that Scala 2.9.1 and 2.9.2 support is dropped.
Would you fix build and travis configurations?

[wookietreiber]

I thought about renaming because the new name fits better, but I revert.

[gakuzzzz]

awesome!

I agree that ConversionImplicits is natural name.
But, it is a cause of discomfort that richSDuration is added into DateImplicits.
I think that is more better creating ScalaDurationImplicits instead of adding into DateImplicits.
What would you say?

cc/ @kmizu @xuwei-k @tototoshi @seratch

[gakuzzzz]

Cool, LGTM.
I want to merge this.
Can I do it, @kmizu ?

[xuwei-k]

👍