vpc module: add backward-compatible support for Python 3.3+
allow dict instances in all filters param, and fix tests by using an OrderedDict
move filters compatibility code to EC2Connection.build_filter_params
Merge pull request #2399 from felixonmars/vpc-py3

vpc module: add backward-compatible support for Python 3.3+. Fixes #2399.
ec2 module: add backward-compatible support for Python 3.3+
fix test_describe_snapshots by using OrderedDict
Merge pull request #2424 from felixonmars/ec2-py3

ec2 module: add backward-compatible support for Python 3.3+. Fixes #2424.