Add command still works and references AB contacts

[nus-se-bot]

Describe the bug
Add command still works and references AB contacts. Similar to #206. Upon further testing, this problem also exists for other AB4 commands such as "list".

To Reproduce
Steps to reproduce the behavior:

1. Open JAR file
2. Type "add"

Expected behavior
Nothing. The add command is not included in the user guide.

Screenshots

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Reported by: @DoItTomorrow
Severity: Low

_{[original: nus-cs2103-AY1819S2/pe-dry-run#240]}

[ghost]

Fixed with #195.