Add file uploads to my existing Ruby on Rails website

I have an existing, open source, two-page website at http://www.dactyl.in. It currently allows users to paste text into a text field and submit the form, where the backend analyzes the text and spits out a bunch of information for them. I would like to add the ability to upload DOC, DOCX, TXT, RTF, and PDF files for the same analysis (while leaving the functionality to also use the direct text input). You can ignore formatting (boldness, italics, headers, tables, headers, footers, etc) in any of the above and just pipe the full document text in as if it should all be analyzed. There's no need to store the file locally when uploaded; it can be kept in memory for analysis, as the original uploaded content does not need to be saved -- just the analysis. You can use whatever gems or libraries you want as long as it runs on Heroku. Files up to 100MB should be supported (ignoring Heroku's upload timeout time); if this is an issue, we can talk and can probably decide on a slightly smaller maximum file size. You will be adding the file upload form as well as the backend form submit processing that pulls the file's contents out and calls the existing analysis framework with them. The project is open source and hosted on GitHub. In order to complete the project, I would like you to clone that project and work in a branch, which can either then be pull requested into master or the entire repository zipped up and delivered through Freelancer. I will also be working in the repo on other issues and will be more than happy to help out if you have any questions, comments, or concerns. Looking forward to working with you!