Django sessions TTL support
Fix docs quotes
Added regression test for numerical string keys.
Fixed #238: dictfields handle numerical strings indexes.
Fix for issue #237: clearing changed fields recursively in EmbeddedDocuments after saving a Document
Add testcase for issue #237
Changed dereference.py to keep tuples as tuples
added unit test for dereference patch
Added LongField to support 64-bit integer type.
Added test cases for LongField.
Fixed potential overflow error.
Revert "Fixed potential overflow error."

This reverts commit 67182713d96233d3d2feb0f67d39ddaf1789c692.
only mark a field as changed if the value has changed

Prevents spurious changes from being recorded.
explicitly check for Document instances when dereferencing

In particular, `collections.namedtuple` instances also have a `_fields`
attribute which confuses the dereferencing.
more ordering unit tests
show that order_by followed by limit works, but not the other way around
Store ordered list of field names, and return the ordered list when iterating a document instance.
Allow construction of document instances using positional arguments.
Tests for construction using positional parameters.
Added kwargs to doc.save to help interop with django (#223, #270)