chore(release): add standard-version & scripts

[joshwiens]

What kind of change does this PR introduce?

Chore

Did you add tests for your changes?

If relevant, did you update the README?

Summary

• Add standard-version part of the webpack-defaults tool set for changelog generation
• Fix Coverage badge in Readme
• Fix Minimum NodeJS version ( 4.3 )

Does this PR introduce a breaking change?

Other information

[codecov]

Codecov Report

Merging #446 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #446   +/-   ##
======================================
  Coverage    98.4%   98.4%           
======================================
  Files           9       9           
  Lines         314     314           
  Branches       71      71           
======================================
  Hits          309     309           
  Misses          5       5

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