Added support for nested fields in dbref_includes Meta attribute.
Merge branch 'pep8' of github.com:orgkhnargh/blitzdb into orgkhnargh-pep8

Thanks Dmytro :)

Conflicts:
	blitzdb/backends/base.py
	blitzdb/document.py
Update README.md
v0.2.5: Bugfix release.
Merge branch 'master' of github.com:adewes/blitzdb
performed flake8 scan and fixed almost all of it's warnings