Fix `mongoose.models` consistency bug.

Since `mongoose.models` and `mongoose.connection.models` weren't the
same object, calling `doc.db.modelNames()` didn't return the same output
as calling `mongoose.modelNames()` even if `doc` was an instance of a
`Model` registered to the default connection.

This caused weird problems when using discriminators, since they are
registered with `parentModel.db.model(...)` (which is equal to
`mongoose.connection`) rather than with `mongoose.model(...)`. Using
discriminators, `mongoose.models` ended up having the parent models'
references, while `mongoose.connection.models` had the discriminators
references.

The fix was to set the default connection's `models` property to
`mongoose.models` so that they share the same object. This makes
`mongoose.models` and `mongoose.connection.models` (or
`document.db.models`, `model.db.models`, `model.base.models` etc.)
deterministically equal.
Fixed missing directory.
Merge pull request #2197 from yamadapc/3.8.x

Fix `mongoose.models` consistency bug.
Merge pull request #2198 from karbassi/patch-1

Fixed missing directory.
Fix memory leak with nested objects #1565
Make copied properties non-enumerable to match previous behavior

Since all properties used to be added to the prototype instead of locally, Object.keys wouldn't catch them.  Now they are added as local properties of the object, so Object.keys picks them up.  Making these properties non-enumerable fixes this, to ensure backward compatibility for people who depended on this behavior.
Fix #2140: bad crash in documentarray.js
Fix #2143: pass back all parameters in promise.resolve
Fix #2187: add .cursor() helper for aggregation to enable agg cursor
Fix #2183: bump node-mongodb-version to 1.4.7
Fix #2151
Wrap up #2151
release 3.8.14
createdAt and updatedAt date attributes
Now working on 3.8.15
Merge pull request #2211 from devongovett/memory-leak

Fix memory leak with nested objects #1565
Tests and POC for #2176
Fix #2176: get rid of buggy and unnecessary caching of _id for populated. Also related to #1794
Merge branch '3.8.x' of github.com:LearnBoost/mongoose into 3.8.x
Merge pull request #2227 from aanfuso/timestamps

createdAt and updatedAt date attributes