update mocha to 3.1.2 (#11625)

tests/UI/config.dist.js

tests/lib/mocha-3.1.0/.eslintignore

tests/lib/mocha-3.1.0/.eslintrc

tests/lib/mocha-3.1.0/lib/browser/debug.js

tests/lib/mocha-3.1.0/test/acceptance/duration.spec.js

tests/lib/mocha-3.1.0/test/acceptance/glob/glob.spec.js

tests/lib/mocha-3.1.0/test/acceptance/misc/nontty.spec.js

tests/lib/mocha-3.1.0/test/acceptance/require/a.js

tests/lib/mocha-3.1.0/test/acceptance/require/c.js

tests/lib/mocha-3.1.0/test/browser/array.spec.js

tests/lib/mocha-3.1.0/test/browser/stack-trace.spec.js

tests/lib/mocha-3.1.0/test/fixture-expect.js

tests/lib/mocha-3.1.0/test/hook-async.spec.js

tests/lib/mocha-3.1.0/test/hook-sync.spec.js

.../integration/fixtures/options/async-only-async.fixture.js

...t/integration/fixtures/options/async-only-sync.fixture.js

...a-3.1.0/test/integration/fixtures/options/grep.fixture.js

...1.0/test/integration/fixtures/options/only/tdd.fixture.js

....0/test/integration/fixtures/options/sort-beta.fixture.js

...ntegration/fixtures/regression/1794/issue-1794.fixture.js