Do not trim output whitespace prefix

Whitespace prefix of output lines was carried over from the old v1
version, but in some cases it removes too much whitespace. Ideally it
would detect the common prefix of all output lines for a given text and
only trim that. Until that's fixed, let's just stop removing the
whitespace.

Fixes #131

junit/junit.go

@@ -259,7 +259,7 @@ func formatBenchmarkTime(d time.Duration) string {
 func formatOutput(output []string, indent int) string {
 	var lines []string
 	for _, line := range output {
-		lines = append(lines, gtr.TrimPrefixSpaces(line, indent))
+		lines = append(lines, line)
 	}
 	return strings.Join(lines, "\n")
 }