Make parser handle nested tests correctly

I use [testify/suite](https://github.com/stretchr/testify#suite-package) to write my tests.
It cause `go test` generate nested test report like:
```
=== RUN TestSuite
=== RUN TestNestedTest1
--- PASS: TestNestedTest1 (0.00 seconds)
=== RUN TestNestedTest2_WithMessage
--- PASS: TestNestedTest2_WithMessage (0.00 seconds)
	goconvey_server_parser_test.go:26: Some Log Message
=== RUN TestSkip
--- SKIP: TestSkip (0.00 seconds)
	goconvey_server_parser_test.go:18: Skip this
--- PASS: TestSuite (0.00 seconds)
PASS
ok  	github.com/wancw/goconvey/examples	0.044s
```
but is considered fail by the GoConvey parser.

So I create this pull request to make parser work as expected.