Update RVM

$ rvm get head

List current versions, and all versions

$ rvm list
$ rvm list known

Select the version you want to upgrade to :

$ rvm upgrade 1.9.3

Are you sure you wish to upgrade from ruby-1.9.3-p125 to ruby-1.9.3-p194? (Y/n): Y  
...
Are you sure you wish to MOVE gems from ruby-1.9.3-p125 to ruby-1.9.3-p194?
This will overwrite existing gems in ruby-1.9.3-p194 and remove them from ruby-1.9.3-p125 (Y/n): Y