refactor(Server): use class

[hiroppy]

• This is a bugfix
• This is a feature
• This is a code refactor
• This is a test update
• This is a docs update
• This is a metadata update

For Bugs and Features; did you add new tests?

Motivation / Use-Case

Cherry-pick from #1657 .

Breaking Changes

no

Additional Info

[hiroppy]

@evilebottnawi Could you restart Travis CI because I don't have an access right?

[alexander-akait]

Looks good, but it is breaking change, we can do this only in next major release 😞 I am wrong

[codecov]

Codecov Report

Merging #1658 into master will decrease coverage by 0.49%.
The diff coverage is 76.96%.

@@            Coverage Diff            @@
##           master    #1658     +/-   ##
=========================================
- Coverage   75.62%   75.12%   -0.5%     
=========================================
  Files          18       18             
  Lines         603      591     -12     
  Branches      171      171             
=========================================
- Hits          456      444     -12     
  Misses        113      113             
  Partials       34       34

Impacted Files	Coverage Δ
lib/Server.js	78.49% <76.96%> (-0.68%)	⬇️

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