Rule proposal: no pending tests

[catkins]

Inside a large mocha test suite, it's quite difficult to hunt down pending specs of PRs past. It would be awesome to be able to mark them as warnings to pester each other to implement or delete them.

OK

describe('some module', function() {
  it('implements a test', function() {
    expect(true).to.be.ok;
  });
});

Error

describe('some module', function() {
  it('does not yet implement a test');

  it.skip('implemented but skipped', function() {
    expect(false).to.be.ok;
  });
});

describe.skip('another module', function() {
  // ...
});

[lo1tuma]

Sounds good to me.

[lo1tuma]

Implemented in #59 and released with version 2.2.0.