Improve CLI ergonomics

[jandelgado]

• summarize common option like TLSOPTIONS and COMMON OPTIONS for better readbility
• remove redundant explanations for DURATION

[coveralls]

Pull Request Test Coverage Report for Build 19411352409

Details

• 14 of 30 (46.67%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.3%) to 86.103%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
cmd/rabtap/main.go	2	5	40.0%
cmd/rabtap/command_line.go	12	25	48.0%

Files with Coverage Reduction	New Missed Lines	%
cmd/rabtap/command_line.go	1	84.22%

Totals
Change from base Build 19389423634:	-0.3%
Covered Lines:	2720
Relevant Lines:	3159

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💛 - Coveralls