feat: Automatic argument mounting

[k-kinzal]

Derived from #17.

Proposal

/bin/curl:
  image: tutum/curl
  tag: alpine
  experimental: true
  entrypoint: curl

$ curl ... -O $HOME/Downloads
$ cat $HOME/Downloads/[your download file]

We propose mounting the path specified by the argument.

• host: Always mount if the argument contains a path
• guest: If mounted on guest mount it. Otherwise, a warning is displayed.

However, this is complicated.
Therefore we want to work only when experimental flag is enabled.
If it stabilizes, remove the flag of experimental to make it the default behavior.