Rough contributing doc added

CONTRIBUTING.md

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+# How to Contribute
+
+## Reporting Issues
+
+Issues can be reported via the [Github Issues](https://github.com/donatj/PhpUserAgent/issues) page.
+
+- **Detail is key**: If a browser is being misidentified, one or more sample user agent strings are key to getting it resolved.
+- **Missing Browser**: Is it modern? What is it being misidentified as? There are a lot of dead browsers out there that there is no reason to support.
+
+Please do not file any requests for OS identification. 
+
+## Pull Requests
+
+Pull requests are truly appreciated. While I try my best to stay on top of browsers hitting the market it is still a difficult task.
+
+- **Formatting**: Indentation **must** use tabs. Please try to match internal formatting and spacing to existing code.
+- **Tests**: If you're adding support for a new browser be sure to add test user agents for if at all possible ***every platform*** the browser is available on. Untested code will take much longer to be merged.
+- **Terseness**: Try to be terse. Be clever. Take up as little space as possible. The point of this project initially was to be smaller than the other guys.