Add CONTRIBUTING guide

[Closes #14]

CONTRIBUTING.md

@@ -0,0 +1,32 @@
+## Contributing to Rambling Trie
+
+1. If you have found a bug or have a feature request, please [search through the issues][github_issues_all] to see if it has already been reported. If that's not the case, then [create a new one][github_issues_new] with a full description of what you have found or what you need.
+1. If you have bug fix or a feature implementation in mind, then [fork Rambling Trie][github_fork] and create a branch with a descriptive name.
+1. Get the gem up and running locally (tests are written in RSpec):
+
+    ```sh
+    bundle install
+    rake
+    ```
+
+1. Implement your bug fix or feature - ***make sure to add tests!***
+1. [Make a Pull Request][github_pull_request]
+
+    Before doing so:
+
+    ```sh
+    git remote add upstream git@github.com:gonzedge/rambling-trie.git
+    git checkout master
+    git pull upstream
+    git checkout my-feature-branch
+    git rebase master
+    git push --set-upstream origin my-feature-branch
+    ```
+
+Feel free to reach out to [@gonzedge][github_user_gonzedge] with any questions.
+
+[github_fork]: https://help.github.com/articles/fork-a-repo
+[github_issues_all]: https://github.com/gonzedge/rambling-trie/issues?utf8=%E2%9C%93&q=is%3Aissue
+[github_issues_new]: https://github.com/gonzedge/rambling-trie/issues/new
+[github_pull_request]: https://help.github.com/articles/creating-a-pull-request
+[github_user_gonzedge]: https://github.com/gonzedge

README.md

@@ -203,7 +203,7 @@ The Rambling Trie has been tested with the following Ruby versions:
 
 ## Contributing to Rambling Trie
 
-Take a look at the [contributing guide][rambling_trie_contributing_guide] to get started, or fire a question to [@gonzedge][github_user_gonzedge]
+Take a look at the [contributing guide][rambling_trie_contributing_guide] to get started, or fire a question to [@gonzedge][github_user_gonzedge].
 
 ## License and copyright