Use options pattern instead of config

[philipch07]

Description

Uses the options pattern instead of the config pattern, which is a necessary change before adding SNAP (#449).

Reference issue

Resolves #446

[JoTurk]

yeah this is a good direction, we need to add more validations tho.

[codecov]

Codecov Report

❌ Patch coverage is 18.34862% with 89 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.72%. Comparing base (767b9c4) to head (aa606bd).

Files with missing lines	Patch %	Lines
association_options.go	0.00%	56 Missing ⚠️
association_rack_options.go	0.00%	26 Missing ⚠️
association.go	74.07%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #450      +/-   ##
==========================================
- Coverage   83.79%   82.72%   -1.07%     
==========================================
  Files          52       54       +2     
  Lines        4054     4145      +91     
==========================================
+ Hits         3397     3429      +32     
- Misses        481      539      +58     
- Partials      176      177       +1     

Flag	Coverage Δ
go	82.72% <18.34%> (-1.07%)	⬇️

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[JoTurk]

looks good, i think we'll just need to add test coverage and make newAssociationWithOptions public

[JoTurk]

^ mean making newAssociationWithOptions through new APIs to construct Client and Server.