Update Docs for File Attachment and Docstring Fill

The README docs were missing the trailing colon for the `I fill in "..." (with|for)` step. A `rake update_readme` fixes this issue. Also included was a slight update to the docs for a file attachment step.
Merge pull request #33 from trianglegrrl/fix-docs-for-docstring-fill-in

Update Docs for File Attachment and Docstring Fill