HttpWebRequest/HttpClient and WebClient integration tests

This PR adds several integration tests for HttpWebRequest/HttpClient and WebClient to make sure the purified uri we give these classes also results in a "purified" request to the server. 

It does this by doing requests to http://request-path.herokuapp.com

The source code of which is here:

https://github.com/Mpdreamz/request-path

Interestingly deploying this on azure: http://request-path.azurewebsites.net/hello%2F-world/

vs heroku: http://request-path.herokuapp.com/hello%2F-world/

yields different results! `%2F` truly is the bane of the microsoft stack :)

PS: if you want access to the herokuapp/git repos let me know!


PS PS: this PR also moved the extension method from the `Purify` namespace to the `PUrify` namespace. I'm not sure if the lowercase `u` was intentional or not? If so I'll need to ammend this PR.