docs(README): standardize

[michael-ciniawsky]

README

• Styling && Format
• uglify-es changes (options.uglifyOptions)

Closes #27

[codecov]

Codecov Report

Merging #61 into master will not change coverage.
The diff coverage is n/a.

@@         Coverage Diff          @@
##           master   #61   +/-   ##
====================================
  Coverage       0%    0%           
====================================
  Files           2     2           
  Lines         132   132           
  Branches       46    46           
====================================
  Misses         91    91           
  Partials       41    41

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[kzc]

uglify-es changes (options.uglifyOptions)

All occurrences of:

https://github.com/mishoo/UglifyJS2/tree/master

should be replaced with:

https://github.com/mishoo/UglifyJS2/tree/harmony

as the former is uglify-js and the latter is uglify-es.

uglify-es has additional documented options such as ecma and safari10