Show list of available rubies,

## Usage:

    rvm list [help,known,remote [|rbx|jruby|all],gemsets,default [string],rubies,strings,known_strings,ruby_svn_tags]

## Actions:

- `help`    - show this help
- `known`   - list known rubies, that can be installed
- `gemsets` - list all rubies with their gemsets
- `rubies`  - list installed rubies, it is the default action when none given
- `strings` - list installed rubies, machine passable form
- `known_strings`    - list known rubies, that can be installed, machine passable form
- `ruby_svn_tags`    - list ruby tags available at http://svn.ruby-lang.org/repos/ruby/tags/
- `default [string]` - show the default ruby, passable form with strings
- `remote [|rbx|jruby|all]` - list binary build rubies (also for all/rbx/jruby), they do not need compilation,
                              when parameter omitted then only rvm build binaries are listed.