📝 Add guide for converting a TextMate bundle

docs/converting-a-textmate-bundle.md

@@ -0,0 +1,50 @@
+## Converting a TextMate Bundle
+
+This guide will show you how to convert a [TextMate][TextMate] bundle to an
+Atom package.
+
+Converting a TextMate bundle will allow you to use its editor preferences,
+snippets, and colorization inside Atom.
+
+### Install apm
+
+The `apm` command line utility that ships with Atom supports converting
+a TextMate bundle to an Atom package.
+
+Check that you have `apm` installed by running the following command in your
+terminal:
+
+```sh
+apm help init
+```
+
+You should see a message print out with all the possible `apm` commands.
+
+If you do not, launch Atom and run the _Atom > Install Shell Commmands_ menu
+to install the `apm` and `atom` commands.
+
+### Convert the Package
+
+Let's convert the TextMate bundle for the [R][R] programming language. You can find other existing TextMate bundles [here][TextMateOrg].
+
+You can convert the R bundle with the following command:
+
+```sh
+apm init --package ~/.atom/packages/language-r --convert https://github.com/textmate/r.tmbundle
+```
+
+You can now browse to `~/.atom/packages/language-r` to see the converted bundle.
+
+:tada: Your new package is now ready to use, launch Atom and open a `.r` file in
+the editor to see it in action!
+
+:bulb: Consider using `apm publish` to publish this package to
+[atom.io][atomio].
+
+[atomio]: https://atom.io
+[CSS]: http://en.wikipedia.org/wiki/Cascading_Style_Sheets
+[LESS]: http://lesscss.org
+[plist]: http://en.wikipedia.org/wiki/Property_list
+[R]: http://en.wikipedia.org/wiki/R_(programming_language)
+[TextMate]: http://macromates.com
+[TextMateOrg]: https://github.com/textmate/r.tmbundle