Add kwargs, redirect 'region' to 'Region'.

Add kwargs to AmazonAPI constructor.
kwargs are passed directly to bottlenose.Amazon(...).
This allows access to MaxQPS and other niceties.
Provide a 'region'->'Region' redirect so old code
won't break. New code should use the bottlenose Region
property.
Add tests for region, Region and MaxQPS.
Update README to use Region= not region=
Merge pull request #38 from adamlwgriffiths/master

Add kwargs, redirect 'region' to 'Region'.