Merge branch 'release/1.21.0'
fix handling CTRL+C in __rvm_ask_for, fix #1974
fix detecting osx version when only 10.9 is used, update #1975
fix the missing binary message
fix detecting default/global gemset initalization, fix #1976
1.21.1
Merge branch 'master' into hotfix/1.21.1
Merge branch 'hotfix/1.21.1' into stable