Combining the coverprofiles to one file should remove the mode (mode: xxx) line

[27149chen]

When combining the coverprofiles to one file, ginkgo should remove the mode (mode: xxx) line, it is the first line in every single profile. Otherwise, running "go tool cover -html=" will report "cover: line [] doesn't match expected format: ^(.+):([0-9]+).([0-9]+),([0-9]+).([0-9]+) ([0-9]+) ([0-9]+)$"

Using ginkgo 1.6

[williammartin]

Hi. Would welcome a PR to fix this if you are up for it.