Separate user interrupt and terminating due to errors in SessionOutome

[fjarri]

Fixes #19

terminate_due_to_errors() is kind of an awkward name, but I can't come up with anything better now.

Maybe we'll be able to select the reason automatically when #15 is fixed.

[coveralls]

Pull Request Test Coverage Report for Build 11601312655

Details

• 15 of 16 (93.75%) changed or added relevant lines in 2 files are covered.
• 8 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.3%) to 71.483%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
manul/src/session/session.rs	14	15	93.33%

Files with Coverage Reduction	New Missed Lines	%
manul/src/protocol/errors.rs	3	21.21%
manul/src/session/session.rs	5	76.58%

Totals
Change from base Build 11600676687:	-0.3%
Covered Lines:	1514
Relevant Lines:	2118

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💛 - Coveralls