修改sublime列编辑快捷键

这个问题在好几个电脑上搞了好几次，每次都要搜搜，记录备忘。

Ubuntu的sublime列编辑修改为简单的快捷键：

路径：Preferences→Key Bindings

默认是

	{ "keys": ["alt+shift+up"], "command": "select_lines", "args": {"forward": false} },
	{ "keys": ["alt+shift+down"], "command": "select_lines", "args": {"forward": true} },

可以在右侧的User自定义部分覆盖默认配置，修改为alt+上/下，也就是：

[
	
	{ "keys": ["alt+up"], "command": "select_lines", "args": {"forward": false} },
	{ "keys": ["alt+down"], "command": "select_lines", "args": {"forward": true} }
]