Introduces the ability to permanently delete a user (intercom#251)

This change introduces a new `archiveUser` method, and updates the
`deleteUser` method to alias it.

Additionally the change introduces a new `permanentlyDeleteUser`
that leverages a `POST` to `user_delete_requests` to initiate
a permanent delete from the intercom api.

Addresses: intercom#249

added scroll for leads (intercom#238)

ran phpcbf to fix indenting and commenting inconsistencies (intercom#233

)

Lucianocn master (intercom#232)

* improved .gitignore

* added extraGuzzleRequestsOptions (optional) to IntercomClient

* avoid $extraGuzzleRequestsOptions errors

* typo fixes

* Adding unit test for PR intercom#206 and fixing unit test from previous PR

* Removing misc print and setting test timezone to UTC

* Fixing issue with CI test failing

Merge pull request intercom#230 from intercom/readme_rate_limit

Adding readme updates for rate limit PR

Merge pull request intercom#229 from intercom/readme_update

Adding example for viewing segment

visitor endpoint / fixes / getConversation option for display_as

Merge pull request intercom#201 from fnwbr/patch-1

Use correct PHPdoc types for user IDs

Update companies/users/leads

add GET segment