Add gitconfig info to Contributing Guide

and write GitHub instead of Github.

[skip ci]

CONTRIBUTING.md

@@ -81,20 +81,24 @@ Here's a quick guide:
 8. Update the Change Log. If you are adding new functionality, document it in
    the README.
 
-9. Commit your changes (`git commit -am 'Add feature/fix bug/improve docs'`).
+9. Make sure git knows your name and email address in your `~/.gitconfig` file:
 
-10. If necessary, rebase your commits into logical chunks, without errors. To
+        $ git config --global user.name "Your Name"
+        $ git config --global user.email "contributor@example.com"
+
+10. Commit your changes (`git commit -am 'Add feature/fix bug/improve docs'`).
+   If your pull request only contains documentation changes, please remember
+   to add `[skip ci]` to the beginning of your commit message so the Travis
+   test suite doesn't :runner: needlessly.
+
+11. If necessary, rebase your commits into logical chunks, without errors. To
    interactively rebase and cherry-pick from, say, the last 10 commits:
    `git rebase -i HEAD~10`, then `git push -f`.
 
-11. Push the branch up to your fork on Github
-   (`git push origin my-new-feature`) and from Github submit a pull request to
+12. Push the branch up to your fork on GitHub
+   (`git push origin my-new-feature`) and from GitHub submit a pull request to
    Ransack's `master` branch.
 
-12. If your pull request only contains documentation changes, please remember
-   to add `[skip ci]` to the beginning of your commit message so the Travis
-   test suite doesn't :runner: needlessly.
-
 At this point you're waiting on us. We like to at least comment on, if not
 accept, pull requests within three business days (and, typically, one business
 day). We may suggest some changes or improvements or alternatives.