Vimana::Installer->install( 'package name' );
    Vimana::Installer->install_from_url( 'url' );
    Vimana::Installer->install_from_rcs( 'git:......' );
    Vimana::Installer->install_from_dir( '/path/to/plugin' );

For Text type installer, inspect content like this:

    " Script type: plugin
    " Script dependency:
    "   foo1 > 0.1
    "   bar2 > 0.2
    " 
    " Description:
    "   ....

todo

XXX: some checking method for file-based or dir-based install for install_from_path function. to let this work:

      vimana install path/to/zencoding.vim --name zencoding  
              # package name could be parsed from script file content
      vimana install path/to/dir   --name zencoding