avm use should support sloppy input

[schultyy]

Given I have the following versions installed:

$ avm ls
- 4.2.0
- 4.2.1
- 5.0.0

I want to be able to avm use 5.0.0 by just typing:

$ avm use 5.0

When there are multiple options:

$ avm use 4.2
Multiple versions apply:
- 4.2.0
- 4.2.1