WIP commit.  Lots of changes to facilitate S3 and other REST services.
Changing type of UserData from string to blob to force base64 encoding.  Fixes #19.  Again.
PutObject and GetObject are both working at the botocore level.  Still not handling ContentMD5.  Reworked the tutorial a bit and added some content for streaming input/output.
Need to decode the output of base64.b64encode.
Updating S3 model and adding a couple more unit tests.
Set credentials in environment variables for s3 tests so we don't get an error when we create an endpoint.
Remove unicode prefix from keys in results dict.
Account for header-based parameters that don't have a location_name attribute.
Fixing \n characters inside XML elements in doc strings.