Flesh out the README.md.

README.md

@@ -1,2 +1,30 @@
 # http-client-info
-A class which provides information about the client making an HTTP request
+A simple class which provides information about the client making an HTTP request.
+
+## Installation
+
+This class requires PHP 5.2 or later, but we recommend using the latest available version of PHP as a matter of principle.  It has no dependencies.
+
+It is installable and autoloadable via Composer as [cxj/http-client-info](https://packagist.org/packages/cxj/http-client-info)
+from [Packagist](https://packagist.org/).
+
+Alternatively, [download a release](https://github.com/cxj/http-client-info/releases)from GitHub, or clone this repository.  Then require or include its _autoload.php_ file.
+
+## Quality
+
+This class attempts to comply with [PSR-1][], [PSR-2][], and [PSR-4][]. If
+you notice compliance oversights, please send a patch via pull request.
+
+[PSR-1]: https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-1-basic-coding-standard.md
+[PSR-2]: https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-2-coding-style-guide.md
+[PSR-4]: https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-4-autoloader.md
+
+This package is unit tested using [PHPUnit](https://phpunit.de).
+
+
+## Contributing
+
+Pull requests are welcome!
+
+Requests which follow the PSR-1 and PSR-2 coding and style standards, and which
+have PHPUnit test coverage will get most attention.