Add carrierwave gem.
Migration: add code file to iterations.
Add code_file to Iteration's attr_accessible.
"rails g uploader IterationCodeFile".
Mount iteration code file uploader to Iteration.
Change snippet form to only use file field for nested iteration form.
Replace IterationCodeFileUploader with CodeFileUploader.
Fix Snippet's nested Iteration form to do things properly.
Add github-linguist gem.
Set iteration and snippet values before save from file.
Use fallback text language for Prism if no language detected.