Fix stack cleaning

[sindresorhus]

On Node.js 6 we're not cleaning all the unnecessary stack lines. Needs to be fixed in an external module: tapjs/stack-utils#14 (comment)

[sotojuan]

Does your recent clean-stack module not help with this?

[sindresorhus]

@sotojuan No, we're using another more advanced module in AVA. Should be very easy to fix in stack-utils though. Just need to support / in the stack path.

[LasaleFamine]

This should be solved with 1.0.0 of stack-utils: tapjs/stack-utils#14 (comment).

[novemberborn]

@LasaleFamine thanks for noticing this!