Port to 2.x

[Froussios]

I've recently spent some time designing some minimal changes to this book, so that it is updated to newer versions of Rx.

I understand that this has been a personal project so far. If I were to update this project, would you be interested? I don't want to host a modified version myself, since this is mostly not my work.

[LeeCampbell]

Would love to take some changes.

I have started porting the content to markdown, so that it is easier for others to contribute. However I dont have a build that will update the existing website. You may have noticed that the site is ready to host multiple versions as the version of the build is in the URL eg. v1.0.10621.0 in http://introtorx.com/Content/v1.0.10621.0/01_WhyRx.html#WhyRx

I also want to keep in mind that there will probably be a massive need for rewrite once Rx3.0 is out (which it should be shortly).

The key areas I wanted to address, but never had time was the integration with Task<T>, async/await and an improved section on the testing e.g. TestScheduler, ReactiveTest etc.