added a wrapper to aggregate in Queryset.aggregate
refs #703, added changelog
Merge pull request #703 from wpjunior/aggregate-framework

Simple aggregation framework wrapper
Merge branch 'master' of https://github.com/MongoEngine/mongoengine
Added retry in apt-get operations for travis
Added initial CachedReferenceField
fixes for rebase branch
added CachedReferenceField restriction to use in EmbeddedDocument
refs #709, added CachedReferenceField.sync_all to sync all documents on demand
refs #709, fix typos
refs #709, added support to disable auto_sync
fixes for python2.6
Updated Django development version in the build matrix.
added documentation about CachedReferenceField
Update README.rst
Merge pull request #718 from mbalasso/patch-1

Update README.rst
Fixed typo.
Merge pull request #720 from pashadia/master

Fixed typo.
small fixes for python2.6
Merge pull request #709 from wpjunior/cached-reference-field

CachedReferenceField implementation