Add lint rules for `=>` (fat arrow) and `.` (string concatenation)

Summary: We have coverage for normal binary operators, but not these unusual cases.

Test Plan: Added and executed unit tests.

Reviewers: btrahan, joshuaspence

Reviewed By: joshuaspence

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D9314
Add a version number to `ArcanistXHPASTLinter`.

Summary: Fixes T5209. It makes sense for the `ArcanistXHPASTLinter` to implement the `getVersion` method in order to be able to enforce version requirements (as in T4954).

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Maniphest Tasks: T5209

Differential Revision: https://secure.phabricator.com/D9317
Point github.com/facebook URIs at github.com/phacility (Arcanist Edition)

Summary: See D9328.

Test Plan: `grep`

Reviewers: chad

Reviewed By: chad

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D9329