Add README for documentation of the extension

Author: Brunty

README.md

@@ -0,0 +1,47 @@
+# Behat Speedtrap
+
+[![Build Status](https://travis-ci.org/Brunty/behat-speedtrap.svg?branch=master)](https://travis-ci.org/Brunty/behat-speedtrap)
+
+A smoke testing tool inspired by [symm/vape](https://github.com/symm/vape)
+
+## Installation
+
+Install via composer:
+
+`composer require brunty/behat-speedtrap --dev`
+
+## Configure
+
+In your `behat.yml` file add the following extension configuration:
+
+```yaml
+default:
+  extensions:
+    Brunty\Behat\SpeedtrapExtension: ~
+```
+
+To configure the threshold for slow tests (default 2000ms) specify the configuration option:
+
+```yaml
+default:
+  extensions:
+    Brunty\Behat\SpeedtrapExtension:
+      threshold: 500 # this is in ms
+```
+
+To configure the number of scenarios reported (default 10) specify the configuration option:
+
+```yaml
+default:
+  extensions:
+    Brunty\Behat\SpeedtrapExtension:
+      report_length: 2 
+```
+
+## Contributing
+
+This started as a small personal project.
+
+Although this project is small, openness and inclusivity are taken seriously. To that end a code of conduct (listed in the contributing guide) has been adopted.
+
+[Contributor Guide](CONTRIBUTING.md)