composer 版本问题 [ 2.0 版本 ]

1.报错的内容如下，其实很长一段的问题信息，我只截取最后的部分。

Potential causes:
 - A typo in the package name
 - The package is not available in a stable-enough version according to your minimum-stability setting
   see <https://getcomposer.org/doc/04-schema.md#minimum-stability> for more details.
Read <https://getcomposer.org/doc/articles/troubleshooting.md> for further common problems.

Installation failed, reverting ./composer.json to its original content.

对于新手来讲，出现的很多问题都需要，大量的时间去处理，所以放在这里跟大家说一下，因为我也是新手。
解决措施：1.首先。先更新composer

执行命令 php composer.phar self-update

2.然后更新组件fxp/composer-asset-plugin

执行命令 php composer.phar global require "fxp/composer-asset-plugin:~1.1.1"

这些命令的执行都是放在 cmd 中的
1.C:\Users\USER>php composer.phar self-update 这里是执行的命令

Updating to version 1.4.2 (stable channel).
    Downloading: 100%   下载成功
Use composer self-update --rollback to return to version 1.2.4 版本信息

2.C:\Users\USER>php composer.phar global require "fxp/composer-asset-plugin:~1.1.1" 执行的命令

Changed current directory to C:/Users/USER/AppData/Roaming/Composer
./composer.json has been created
Loading composer repositories with package information
Updating dependencies (including require-dev)
Package operations: 1 install, 0 updates, 0 removals
  - Installing fxp/composer-asset-plugin (v1.1.4): Downloading (100%)  下载成功，安装成功
Writing lock file
Generating autoload files