Vue-material: [new] Expandable input

[marchev]

@marcosmoura First, I would like to thank you for your efforts and this great project!

I believe that the addition of an expandle input (as the one available in MDL's text fields: getmdl.io/components/index.html#textfields-section) would be a good and useful addition to the list of components in the module.

The most common use case is an expandable search field in a toolbar.

[marcosmoura]

This is going to be created in another component, for search bars. I'm closing this issue, but I will develop this really soon. Thank you!