docs: update contributing instructions

.github/CONTRIBUTING.md

@@ -6,14 +6,14 @@ Interested in contributing to Vale? Great—we welcome contributions of any
 
 - [Contributing to Vale](#contributing-to-vale)
   - [Table of Contents](#table-of-contents)
-  - [<a name="intro"></a> Introduction](#-introduction)
-  - [<a name="testing"></a> Testing](#-testing)
-  - [<a name="devenv"></a> Setting up a Development Environment](#-setting-up-a-development-environment)
-  - [<a name="code-guidelines"></a>  Code Contribution Guidelines](#-code-contribution-guidelines)
-  - [<a name="commit-guidelines"></a> Git Commit Message Guidelines](#-git-commit-message-guidelines)
-  - [<a name="terms"></a> Terminology](#-terminology)
+  - [Introduction](#introduction)
+  - [Testing](#testing)
+  - [Setting up a Development Environment](#setting-up-a-development-environment)
+  - [Code Contribution Guidelines](#code-contribution-guidelines)
+  - [Git Commit Message Guidelines](#git-commit-message-guidelines)
+  - [Terminology](#terminology)
 
-## <a name="intro"></a> Introduction
+## Introduction
 
 Vale is a natural language linter that supports plain text, markup (Markdown, reStructuredText, AsciiDoc, and HTML), and source code comments. However, unlike many similar projects, Vale's primary focus isn't on providing a collection of rules everyone must follow&mdash;instead, Vale aims to be flexible enough to support many different styles (see [Styles](https://errata-ai.github.io/vale/styles/) for more information).
 
@@ -27,7 +27,7 @@ More specifically, Vale is written in Go and split into packages that are tasked
 
 If you're looking to improve Vale's documentation, check out the [`docs/`](https://github.com/errata-ai/vale/tree/master/docs) directory.
 
-## <a name="testing"></a> Testing
+## Testing
 
 Vale is tested using both integration and unit tests.
 
@@ -43,20 +43,22 @@ LintMD-2    1.54s ± 1%   1.54s ± 1%    ~     (p=0.604 n=10+10)
 
 To run the tests, you'll want to invoke either `make bench` or `make ci` (see [Setting up a Development Environment]() for more information).
 
-## <a name="devenv"></a> Setting up a Development Environment
+## Setting up a Development Environment
 
-You'll need to have [Ruby](https://www.ruby-lang.org/en/downloads/) (v2.3+) and [Go](https://golang.org/) (v1.7+) installed. Next, you'll need to install and configure [`aruba`](https://github.com/cucumber/aruba) (assuming you're inside the `vale` directory):
+Prerequisites:
+
+* [Ruby](https://www.ruby-lang.org/en/downloads/) (v2.3+)
+* [Go](https://golang.org/) (v1.7+) installed.
+* [Asciidoctor](http://asciidoctor.org/) available on your `$PATH`.
+* [rst2html](http://docutils.sourceforge.net/docs/user/tools.html#rst2html-py) available on your `$PATH`. The latter is installed with both [Sphinx](http://www.sphinx-doc.org/en/stable/) and [docutils](https://pypi.python.org/pypi/docutils).
 
 ```bash
-$ gem install bundler # if necessary
-$ aruba init --test-framework cucumber
+$ gem install bundler:2.2.31 # if necessary
 $ make setup
-$ make ci
+$ make test
 ```
 
-To get all tests passing, you'll also need [Asciidoctor](http://asciidoctor.org/) and [rst2html](http://docutils.sourceforge.net/docs/user/tools.html#rst2html-py) available on your `$PATH`. The latter is installed with both [Sphinx](http://www.sphinx-doc.org/en/stable/) and [docutils](https://pypi.python.org/pypi/docutils).
-
-## <a name="code-guidelines"></a>  Code Contribution Guidelines
+## Code Contribution Guidelines
 
 To make the contribution process as seamless as possible, we ask for the following:
 
@@ -66,7 +68,7 @@ To make the contribution process as seamless as possible, we ask for the followi
     * Squash your commits into a single commit. `git rebase -i`. It’s okay to force update your pull request with `git push -f`.
     * Follow the **Git Commit Message Guidelines** below.
 
-## <a name="commit-guidelines"></a> Git Commit Message Guidelines
+## Git Commit Message Guidelines
 
 Vale follows a modified version of the [AngularJS Commit Guidelines](https://github.com/angular/angular.js/blob/master/CONTRIBUTING.md#-git-commit-guidelines). A commit message should take the following form:
 
@@ -99,7 +101,7 @@ Also demotes `Annotations` and `PassiveVoice` to "suggestions."
 Related to #30.
 ```
 
-## <a name="terms"></a> Terminology
+## Terminology
 
 | Term  | Definition                                                                                                                                                                        |
 |:-----:|:----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|