AsertoError.Fields() includes fields from inner errors

[ronenh]

Prior to #17 the fields of inner errors would be copied into the data field of the outer message, which resulted in error message formatting that appears out of order.

However, with that behavior gone we still want the Fields() function to include fields from inner errors, which is what this commit achieves.

[coveralls]

Pull Request Test Coverage Report for Build 14344599729

Details

• 5 of 11 (45.45%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.7%) to 64.577%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
context.go	0	1	0.0%
errors.go	5	10	50.0%

Totals
Change from base Build 14340657180:	-0.7%
Covered Lines:	206
Relevant Lines:	319

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💛 - Coveralls