I had an EMR step that contained a `&` and this caused the ListStep call to fail.
I've added the `| escape` filter to handle it in this case and a few other cases that look like they could suffer the same fate.
This revision includes:
- A handler for requests for which content-type is JSON (from boto3).
- A decorator (generate_boto3_response) to convert XML responses to
JSON (for boto3). This way, existing response templates for boto can
be shared for generating boto3 response.
- Utility class/functions to use botocore's service specification data
(accessible under botocore.data) for type casting, from query
parameters to Python objects and XML to JSON.
- Updates to response handlers/models to cover more EMR end points and
mockable parameters
