#913: Require FakeOctokit dependencies

[gemshrine]

Fixes #913

Cause

fbe/fake_octokit uses Veil in rate_limit and Octokit::NotFound in its error paths, but the file did not load those dependencies itself. Requiring the documented entry point in a fresh Ruby process therefore failed when one of those methods ran. The file also relied on the Fbe namespace having been loaded by another entry point.

Change

The fake client now requires Octokit, Veil, and the gem's root file directly, so its documented entry point can be used on its own.

Test coverage

A subprocess test starts a fresh Ruby interpreter, requires fbe/fake_octokit, calls rate_limit, and exercises the Octokit::NotFound path. Run it with bundle exec ruby -Itest test/fbe/test_octo.rb --name test_fake_octokit_can_be_required_on_its_own; repository CI also runs the full Rake test suite.

[gemshrine]

Closing this duplicate. PR #917 already addresses #913; I moved the standalone Fbe namespace require and fresh-process regression coverage into #917, which remains the PR for this issue.