Exlude -> Exclude typo
String improvements
Remove duplicate stating of page title

The page title is already given in the first argument of the `add_options_page()` call, so let's re-use that than state it again.
Add i18n to page title and menu label
File-level documentation
Update text domain to match plugin slug

For the future language packs in Wp to work correctly, the text domain on strings should match the plugin slug.
Code standards

Update to use the WordPress Code Standards.
Support GitHub Updater

The GitHub Updater plugin allows plugins to be updated directly from GitHub, just by including a couple of commented lines within the plugin header.

The standard is for GitHub Updater to check for tags, so you should tag each release. If there are no tags, then it will check the branch mentioned (here, master). As such, you should create a branch from master called develop and do all future PRs to that (make developer the default branch via this repo's Settings in the sidebar), which leaves master as the clean / stable version. You're now following the basics of git-flow!
Add documentation

Also corrects the version numbering to 3 digits, as per WP code standards.
Update description to clarify intent.

States what happens if this field is not filled in.
Refactor gfln_parse_footer_links()

 * Renames gfln_parse_footer_links() to gfnl_amend_links(). This is to make it more general, since we don't care where the links are located. The fact they are from a footer has already been decided by filtering genesis_footer_output.
 * Moves the domains grabbing code to own function.
 * Domain grabbing now includes a trim call.
Remove extraneous conditional code

If each conditional is returning something, then no need to check for else, since if the PHP parser has got to the next part, it automatically must be the else state. Keeps the code cleaner and easier to read.
Update plugin description

Just helps clarify what the plugin does.
Load plugin textdomain

This now makes the plugin fully translatable. The .pot file can be generated later.
Create README.md

Makes the repo look better!
Merge pull request #1 from GaryJones/patch-1

General improvements