Required tty on box remove

```
$ pecrant box remove

Vagrant is attempting to interface with the UI in a way that requires
a TTY. Most actions in Vagrant that require a TTY have configuration
switches to disable this requirement. Please do that or run Vagrant
with TTY.
```

Because, situations such as the following may occur:

```
$ vagrant box remove foobar

Box 'foobar' (v0) with provider 'virtualbox' appears
to still be in use by at least one Vagrant environment. Removing
the box could corrupt the environment. We recommend destroying
these environments first:

default (ID: xxxxx)

Are you sure you want to remove this box? [y/N] 
```