try to fix rvm error

/Users/xxx/.rvm/lib/rvm/capistrano.rb:5:in `<top (required)>': RVM -
Capistrano integration was extracted to a separate gem, install: `gem
install rvm-capistrano` and remove the `$LOAD_PATH.unshift` line, note
also the 'set :rvm_type, :user' is now the default (instead of
:system). (RuntimeError)