use jest instead of mocha

[whatwewant]

• Why
  • [look at this] 早报@2019-01-08 whatwewant/yuedu#24

[whatwewant]

it is weird. Cannot find module './lib/source-map-generator' from 'source-map.js'. what's the fuck.

[codecov]

Codecov Report

Merging #9 into master will increase coverage by 0.64%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master       #9      +/-   ##
==========================================
+ Coverage   93.58%   94.23%   +0.64%     
==========================================
  Files           3        3              
  Lines         156      156              
  Branches       26       26              
==========================================
+ Hits          146      147       +1     
  Misses          4        4              
+ Partials        6        5       -1

Impacted Files	Coverage Δ
src/utils.ts	87.5% <0%> (ø)	⬆️
src/index.ts	94.62% <0%> (+1.07%)	⬆️

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