BREAKING CHANGE: Add Strongly-Typed 'InlineResult' Class.

Opening up this pull request so you can have a look. Not added errors yet, since I'm not actually experiencing any since we've prevented the pseudo classes/elements going to CsQuery.

* Added the `Html` property to return the HTML content we're used to.
* Added `Warnings` collection and removed the output of warnings as HTML comments.

### Tasks Pending

- [x] Update the README to include new `InlineResult` usage. Also need to explain issue with pseudo classes/elements and the warnings collection.
- [x] Refactor the internal DSL to remove use of statics so that it can update warnings/errors collections during processing with ease.