Added -grade which automatically uses -json-flat and -rawoutput to show
only the grades, e.g.:

./ssllabs-scan -quiet  -grade -hostfile=./tf 
"testing1.yoursite.com": "A"
"testing4.yoursite.com": "F"
Merge branch 'master' into feature-grade
Merge branch 'master' into feature-grade
Merge branch 'master' into feature-grade
Merge branch 'master' into feature-grade

Conflicts:
	ssllabs-scan.go
Merge pull request #30 from cognusion/feature-grade

Feature grade