Update perf_to_profile cli arguments to use flags. (#277) (#332)

Update perf_to_profile cli arguments to use flags. (#277)

Fixes #277

As perf_to_profile uses flags to parse its arguments, modify the call to perf_to_profile to use flags. Also pass the '-f' flag to overwrite the existing output profile file.
Redirect perf_to_profile's stdout/stderr to pprof's stdout/stderr.

internal/driver/fetch.go

 		return nil, err
 	}
 	deferDeleteTempFile(profile.Name())
-	cmd := exec.Command("perf_to_profile", perfPath, profile.Name())
+	cmd := exec.Command("perf_to_profile", "-i", perfPath, "-o", profile.Name(), "-f")
+	cmd.Stdout, cmd.Stderr = os.Stdout, os.Stderr
 	if err := cmd.Run(); err != nil {
 		profile.Close()
 		return nil, fmt.Errorf("failed to convert perf.data file. Try github.com/google/perf_data_converter: %v", err)