Add event handler to quote the x-amz-copy-source header value as expected by S3.  Fixes https://github.com/aws/aws-cli/issues/614.
Merge pull request #221 from garnaat/fix-awscli-614

Add event handler to quote the x-amz-copy-source header value as expected by S3.
Support one level of nested configs

In the config file you can now say:

    [default]
    key = value
    nested =
        subkey = 1
        other = 2

And it will be parsed as:

    {'key': 'value', 'nested': {'subkey': 1, 'other': 2}}
Add handler to override signature version based on cfg value