Add has to language chains

[duncanbeevers]

Add has to the language chains.

This is to address the awkward phrasing that arises from chaining assertions off of properties.

expect(obj)
  .to.have.property('collection')
  .that.has.members([1, 2, 3])

[coveralls]

Coverage remained the same when pulling 4ea26a7 on duncanbeevers:add_has into 564af34 on chaijs:master.

[vesln]

Fine by me. @logicalparadox ?

[logicalparadox]

👍

[vesln]

Thanks!