completed typedefs for cassowary; switched to cassowary-ts;#1

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fudgepop01 wants to merge 4 commits intoevoL:typescriptfrom

fudgepop01:typescript

Commits on Apr 10, 2019

completed typedefs for cassowary; switched to cassowary-ts; changed ts target to es2017
fudgepop01
committed

Commits on Apr 11, 2019

Commits on Apr 12, 2019

converted all js files to typescript files.
fudgepop01
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