Revert "Link to "learn more" for v3-beta download. Uses horrible CSS hacks that will soon be removed."

This reverts commit c8ebd712aaed5354c2208af0e9eea0f2c4b63057.
Add section to computed about notify extender; clarify meaning of "primitive value"
Update documentation to use allBindings.get instead of allBindingsAccessor.
Update Knockout version so modified live examples work.
The viewModel parameter for binding handlers is deprecated; change to use bindingContext.$data.
Mention that bindings can skip the value part and have an undefined value
Remove section about issues with multiple bindings
Change all instances of ko.utils.unwrapObservable to ko.unwrap
Ensure that spaces in code between different types of highlighting have the correct font.
Fix background color.
initial preprocessing page
Add section on $rawData
Update examples of extend and createChildContext to use a callback functions. Add reference to $rawData.
add documentation of checkedValue parameter
Fix indentation and formatting of value docs
Update computed filtering examples to include .extend({notify:'always'})
Remove example 4 using dynamic binding handlers; add reference
Add comment to clarify `createChildContext` API
Tweak checkedValue example for casing/indentation consistency
Proposed tweaks to writable computeds examples

Let me know if this seems wrong
Clarify value-binding.md to fix #1142
Update value-binding.md

Modify "no binding" example to be more specific