Expose code snippet parameter hash as separate api endpoint

so that we can edit and construct the tag elsewhere
Good question.  When organization.code_snippet returned an HTML string, we just had specs on organization.code_snippet.  But now that it returns a CodeSnippet object, I've split these specs into two logical parts: "organization.code_snippet returns the right object" and "codesnippet works properly"

The intent in this change was that only code_snippet_spec need test the formatting of the HTML string, but organization_spec needs to test that properties of the organization make it into the code snippet.