use whatwg streams

[jimmywarting]

streams are coming to node, might as well prepare for it.

closes #51
closes #101
fixes node v12 - could not use

• fs/promise
• optional changing

[codecov]

Codecov Report

Merging #103 (dbfefe8) into master (4747497) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #103   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            3         3           
  Lines          350       397   +47     
  Branches        51        58    +7     
=========================================
+ Hits           350       397   +47     

Impacted Files	Coverage Δ
from.js	100.00% <100.00%> (ø)
index.js	100.00% <100.00%> (ø)

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