Add a `LINT_CONSTRUCTOR_PARENTHESES` rule to `ArcanistXHPASTLinter`

Summary: Adds an `ArcanistXHPASTLinter::LINT_CONSTRUCTOR_PARENTHESES` rule which ensures that (possibly empty) parentheses are used when calling a constructor.

Test Plan: Added test cases.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D10597
Mark some methods in `ArcanistLinter` as final

Summary: Minor change, self-explanatory... this seems to make sense.

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D10476
Extend `ArcanistXHPASTLinter::LINT_KEYWORD_CASING`

Summary: Extend `ArcanistXHPASTLinter::LINT_KEYWORD_CASING` to include the `class` keyword.

Test Plan: I can't really added a test case for this without getting "XHP19 Class-Filename Mismatch".

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D10653
Fix `LINT_KEYWORD_CASING` for `class` keyword

Summary: D10653 didn't quite cut it.

Test Plan: Tested on a real file.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D10656
Remove gist link that (never?) doesn't work

Summary: Removing 404 link, fixes https://github.com/phacility/arcanist/issues/180

Test Plan: n/a

Reviewers: epriestley, avivey

Reviewed By: epriestley, avivey

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D10689