optimize Sequence for performance by using Promise.each
optimize Sequence for performance by using Promise.each

Previously, Sequence was checking for Promise-type result
every time, to detect when a Promise needs to be returned
from .run() method, which created a deep Promise chain.

After this change, when Sequence finds Promise-type result
it uses Promise.each on all the remaining tests.

Collinslenjo/ava,andywer/ava-ts,avajs/ava,Collinslenjo/ava,BarryThePenguin/ava,sindresorhus/ava,avajs/ava,andywer/ava-ts