Update Tag Command usage in UG

[li-s]

Resolve #221
Resolve #219

[codecov-io]

Codecov Report

Merging #262 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #262   +/-   ##
=========================================
  Coverage     64.50%   64.50%           
  Complexity      550      550           
=========================================
  Files           100      100           
  Lines          1820     1820           
  Branches        189      189           
=========================================
  Hits           1174     1174           
  Misses          572      572           
  Partials         74       74           

Impacted Files	Coverage Δ	Complexity Δ
...ava/seedu/address/logic/commands/ClearCommand.java	100.00% <ø> (ø)	2.00 <0.00> (ø)

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