Add summary at the end of the measurement and fix RTT calc

[robertodauria]

This PR adds a summary at the end of the measurement and fixes the RTT calculations.

Closes #40

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This change is 

[coveralls]

Pull Request Test Coverage Report for Build 7798937328

• -55 of 57 (3.51%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-1.2%) to 68.291%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/client/emitter.go	0	12	0.0%
pkg/client/client.go	2	45	4.44%

Files with Coverage Reduction	New Missed Lines	%
pkg/client/emitter.go	1	0.0%

Totals
Change from base Build 7626914882:	-1.2%
Covered Lines:	883
Relevant Lines:	1293

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💛 - Coveralls

[stephen-soltesz]

Reviewed 3 of 3 files at r1.
Reviewable status: complete! 1 of 1 approvals obtained (waiting on @robertodauria)

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pkg/client/client.go line 100 at r1 (raw file):

	// minRTT is the lowest RTT value observed across all streams.
	minRTT atomic.Uint32

I'm wondering out loud if there's a way to combine the measures for a synthetic measurement (e.g. just avg, or min/avg/max like ping) without dropping some data.