[Bug Report] The end width of el-menu-collapse-transition was hardcoded to '64px'

[lain1936]

Element UI version

2.0.0-alpha.2

OS/Browsers version

chrome

Vue version

2.5.2

Reproduction Link

http://panjiachen.github.io/vue-element-admin/#/dashboard

Steps to reproduce

preset el-menu's width as '36px'

1. click the topleft svg icon to collapse the aside menus
2. el-menu transition to 64px width
3. el-menu jump to 36px width

What is Expected?

can config the width to get smooth animation

What is actually happening?

hardcoded width

animation flicker