Allow `ArcanistLinterTestCase` to find "lint-test" files at an arbitrary depth

Summary: Self-explanatory

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7910
Allow `PhutilUnitTestEngine::getTestsForPaths` to return paths from the library root directory

Summary: Currently, running `arc unit -- src/` returns with `No tests to run`, even if there are test classes in `src/__tests__/`. This diff changes this behaviour so that `arc unit -- src/` executes unit tests in `src/__tests__/`.

Test Plan: N/A. I suppose you could create a file `src/__tests__/SomeTestCase.php` and see for yourself.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7915
Skip unit tests if `ArcanistLinter::getCacheVersion` throws an `ArcanistUsageException`

Summary: Fixes T4288

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Maniphest Tasks: T4288

Differential Revision: https://secure.phabricator.com/D7913
Added test namespace field to `ArcanistUnitTestResult`

Summary: See https://github.com/facebook/libphutil/issues/34

Test Plan: Run `arc unit`

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7952
Added `ArcanistTextLinter::LINT_BOF_WHITESPACE` and `ArcanistTextLinter::LINT_EOF_WHITESPACE`

Summary: This might not be universally desireable, but I found myself writing an additional linter (which I had called `WhitespaceTextLinter`) for the sake of these two linter tests. I figured it may be of use upstream, and so I decided to submit it as a diff. I won't be offended if it is rejected however.

Test Plan: `arc lint` and `arc unit` are both okay with it.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7957
Prompt user for commit message when auto-committing

See: <https://github.com/facebook/arcanist/pull/137>

Reviewed by: epriestley
Merge branch 'master' of https://github.com/facebook/arcanist