add node-addon-api support

[xVanTuring]

This pr replace nan with node-addon-api which will provide a much better compatibility cross modern nodejs

remove support of v4
add support of v12

[codecov]

Codecov Report

Merging #4 into master will not change coverage by %.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master        #4   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            4         4           
  Lines           54        54           
=========================================
  Hits            54        54           

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