Re-add project_root support in alias command

[swalkinshaw]

Fixes #446

@codepuncher @andronocean this looks correct?

With project_root set:

"@development":
  ssh: "example.test"
  path: "/www/examplecom_123/public/current/web/wp"
"@production":
  path: "/www/examplecom_123/public/current/web/wp"
"@staging":
  path: "/www/examplecom_123/public/current/web/wp"

Without project_root set:

"@development":
  ssh: "example.test"
  path: "/srv/www/example.com/current/web/wp"
"@production":
  path: "/srv/www/example.com/current/web/wp"
"@staging":
  path: "/srv/www/example.com/current/web/wp"

[codepuncher]

For some reason, this is removing the ssh key from aliases on any project I try this on!
path seems fine though

[swalkinshaw]

Oops, restored that

[codepuncher]

Perfect! Works fine for me. Thanks!