Update the user guide in accordance with the new feature specification

[aureliony]

Closes #64

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.56%. Comparing base (06250eb) to head (e02ac5a).

Additional details and impacted files

@@            Coverage Diff            @@
##             master      #65   +/-   ##
=========================================
  Coverage     74.56%   74.56%           
  Complexity      388      388           
=========================================
  Files            66       66           
  Lines          1274     1274           
  Branches        103      103           
=========================================
  Hits            950      950           
  Misses          295      295           
  Partials         29       29           

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[yisiox]

LGTM overall, but perhaps some nits to fix

Edit: on further scrutiny, I think list should be included.

[yisiox]

I think we shouldn't use the term id to refer to contacts but rather it works by index.

[yisiox]

LGTM