Bump @zeit/fun to 0.9.0

[styfle]

This bumps the @zeit/fun dependency to the latest version which adds support for nodejs10.x with now dev.

Related to https://github.com/zeit/now-builders/issues/500

[codecov-io]

Codecov Report

Merging #2445 into canary will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           canary    #2445      +/-   ##
==========================================
- Coverage   10.86%   10.86%   -0.01%     
==========================================
  Files         255      255              
  Lines        9127     9123       -4     
  Branches     1008     1007       -1     
==========================================
- Hits          992      991       -1     
+ Misses       8032     8029       -3     
  Partials      103      103

Impacted Files	Coverage Δ
src/util/dev/builder-cache.ts	69.02% <0%> (+1.5%)	⬆️

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