Update translations section in contributing guidelines (donnemartin#61)

Add credits section.  Remove currently non-existent AUTHORS.md.  Fix maintainer copy/paste error.

Author: donnemartin

CONTRIBUTING.md

@@ -42,20 +42,17 @@ If you are not familiar with pull requests, review the [pull request docs](https
 
 ## Translations
 
-Thanks to [The Art of Command Line](https://github.com/jlevy/the-art-of-command-line) for the following translation template.
-
 We'd like for the guide to be available in many languages. Here is the process for maintaining translations:
 
 * This original version and content of the guide is maintained in English.
 * Translations follow the content of the original. Unfortunately, contributors must speak at least some English, so that translations do not diverge.
 * Each translation has a maintainer to update the translation as the original evolves and to review others' changes. This doesn't require a lot of time, but review by the maintainer is important to maintain quality.
-* See the [AUTHORS.md](AUTHORS.md) file for current maintainers.
 
 ### Changes to translations
 
 * Changes to content should be made to the English version first, and then translated to each other language.
 * Changes that improve translations should be made directly on the file for that language. PRs should only modify one language at a time.
-* Submit a PR with changes to the file in that language. Each language has a maintainer, who reviews changes in that language. Then the primary maintainer @jlevy merges it in.
+* Submit a PR with changes to the file in that language. Each language has a maintainer, who reviews changes in that language. Then the primary maintainer @donnemartin merges it in.
 * Prefix PRs and issues with language codes if they are for that translation only, e.g. "es: Improve grammar", so maintainers can find them easily.
 
 ### Adding translations to new languages
@@ -68,3 +65,7 @@ Translations to new languages are always welcome, especially if you can maintain
 * Invite friends to review if possible. If desired, feel free to invite friends to help your original translation by letting them fork your repo, then merging their PRs.
 * Add links to your translation at the top of every README*.md file. (For consistency, the link should be added in alphabetical order by ISO code, and the anchor text should be in the native language.)
 * When done, indicate on the PR that it's ready to be merged into the main repo.
+
+### Translation template credits
+
+Thanks to [The Art of Command Line](https://github.com/jlevy/the-art-of-command-line) for the translation template.