Sharepoint allows you to use numbers as filenames.  I mistakenly passed in a number (instead of a string) as a folder name and Sharepoint sent an error back in response.

However, the error message it returned, was not valid JSON, and thus we fell int
o the rescue JSON::ParserError block in sharepoint-ruby.rb.  I believe this is a
 mistake; it should instead raise a useful error message.  Otherwise it appears that the operation completed properly, when it fact it failed.

I also added a to_s to the file and folder names in the API.

Thanks!