Remove default method

[Phillip9587]

Based on #93

As mentioned in #70 this PR removes the auth() method which just extracted the authorization header from a Node.js IncomingMessage like object and passed it to the parse() method.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (ee70132) to head (9625196).

Additional details and impacted files

@@            Coverage Diff            @@
##            master       #94   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines           48        30   -18     
  Branches        21        11   -10     
=========================================
- Hits            48        30   -18     

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[blakeembrey]

Looks like it'll need to rebase after I merged the TypeScript PR, sorry! Once this lands we can add some benchmarks, tweak the code for perf, and aim for a new major.