Regions

Improved support for working regions.

## Configuring a Default region

`AWS.config` now accepts a `:region` option (defaults to 'us-east-1').  You can set this value globally or on a per service/client.

    # set a new default region
    AWS.config(:region => 'us-west-2')

    # override the default region 
    ec2 = AWS::EC2.new(:region => 'us-west-1')

## Region and RegionCollection

You can now also use the new regions interface to get service objects:

    ddb = AWS.regions['us-west-2'].dynamo_db
    ddb.tables.map(&:name)

The regions collection object is enumerable as well:

    AWS.regions.each.map(&:name)

You can access a region collection from service classes.  These will only enumerate the regions the service operates in.

    # get a full list of dynamo db tables, grouped by region
    AWS::DynamoDB.regions.each do |region|
      puts region.name
      puts region.dynamo_db.tables.map(&:name)
      puts ''
    end

The old style endpoint configuration options are still supported.  These should be considered *deprecated* and will likely be removed in the next major version (2.0).