slowly prepare to drop node 8 support

[bartekleon]

Since Node 8 is ending its life in 2019-12-31, we should slowly start preparing at least 'todo' list (half a year seems to be a short period of time, but we might run out of time).

• I guess all 'promisify' stuff will disappear since node 10 supports promised version of most of functions (in node 10 it's experimental - in node 12 it's stable)

It might be a chance to release Stryker 3.0,
maybe do stuff like: (#1610, #1457), #1589, #1514, #1508, #1472, #1473 try to clean up issues a bit (which are solved, which aren't or won't)

[nicojs]

This is a bit early IMHO 😅

As for your issues.

• Update dependencies + fix issues related with that #1589, Ignore specific mutations #1472, Support VueCli3 with Jest #1473, Question: New stryker utility #1457, perf: reduce next stryker runs #1610 can be done whenever we want. No need to wait for a major release, since they shouldn't require a breaking change.
• Implement mutation switching 👽🔀  #1514 requires a major change in how mutation is done. I've discussed this face to face with @simondel and the easiest thing will be to build it next to the current mutation implementation and let people opt-in with an --expermimentalMutationSwitching command line flag (or something like it). That way we can actually release it before we remove the old implementation while keeping it all backward compatible. I'll update Implement mutation switching 👽🔀  #1514 as well.

@kmdrGroch would you agree with this? In that case, we can just keep this issue open and focus on the removal of all legacy and deprecated code.

[bartekleon]

@nicojs I was thinking also in dropping node 8 support which is a bit breaking (goodbye node8 users). But yea, no need to hurry, just pointing out, in my opinion, things should be done