Add comment field to Deploy Key response data structure

[zahiar]

When you add a deploy key that contains a comment, the Bitbucket API splits out the comment and returns it in a separate comment field in the API.

For example,
key = "ssh-rsa AAAA...=== my@comment.example"

API response

key = "ssh-rsa AAAA...==="
comment = "my@comment.example"

[zahiar]

Tests pass 🎉

go test -v ./tests/deploykeys_test.go
=== RUN   TestDeployKey
=== RUN   TestDeployKey/create
=== RUN   TestDeployKey/get
=== RUN   TestDeployKey/delete
--- PASS: TestDeployKey (6.68s)
    --- PASS: TestDeployKey/create (3.50s)
    --- PASS: TestDeployKey/get (2.49s)
    --- PASS: TestDeployKey/delete (0.69s)
=== RUN   TestDeployKeyWithComment
=== RUN   TestDeployKeyWithComment/create
=== RUN   TestDeployKeyWithComment/get
=== RUN   TestDeployKeyWithComment/delete
--- PASS: TestDeployKeyWithComment (4.39s)
    --- PASS: TestDeployKeyWithComment/create (2.19s)
    --- PASS: TestDeployKeyWithComment/get (1.96s)
    --- PASS: TestDeployKeyWithComment/delete (0.23s)
PASS
ok      command-line-arguments  13.449s

[ktrysmt]

LGTM!