Edited documentation for keys to better match how it interacts with c…

…ontains and have

lib/chai/core/assertions.js

@@ -966,16 +966,22 @@ module.exports = function (chai, _) {
  * ### .keys(key1, [key2], [...])
  *
  * Asserts that the target contains any or all of the passed-in keys.
- * When used in conjunction with `all`, every key that is passed in
- * must exist in the target object. 
+ * Use in combination with `any`, `all`, `contains`, or `have` will affect 
+ * what will pass.
  * 
  * When used in conjunction with `any`, at least one key that is passed 
- * in must exist in the target object. Use without the `any` or `all` 
- * qualifiers is deprecated and will default to `all`. 
+ * in must exist in the target object. This is regardless whether or not 
+ * the `have` or `contain` qualifiers are used. Note, either `any` or `all`
+ * should be used in the assertion. If neither are used, the assertion is
+ * defaulted to `all`.
  * 
- * Finally, use of the `all` qualifier in general requires that the number of
- * keys passed in must match the number of keys in the target object unless
- * the contains qualifier is also used.
+ * When both `all` and `contain` are used, the target object must have at 
+ * least all of the passed-in keys but may have more keys not listed.
+ * 
+ * When both `all` and `have` are used, the target object must both contain
+ * all of the passed-in keys AND the number of keys in the target object must
+ * match the number of keys passed in (in other words, a target object must 
+ * have all and only all of the passed-in keys).
  * 
  * expect({ foo: 1, bar: 2 }).to.have.any.keys('foo', 'baz');
  * expect({ foo: 1, bar: 2 }).to.have.any.keys('foo');