Replace FPM --vendor with --license, and give it the proper value of "Apache-2.0"

Fixes #3372
Mac OSX command for pip was incorrect
Merge pull request #3374 from tianon/fpm-license-vendor

Replace FPM --vendor with --license, and give it the proper value of "Apache-2.0"
Merge pull request #3419 from newzealandpaul/master

Mac OS X command in docs for pip fixed