Updating release NuGet.config
Updating dev NuGet.config
Make CompleteBlock accessible to derived parser
Merge branch 'release' into dev
Add TagHelper parse tree visitor.

- The visitor looks for TagBlock's that match registered TagHelpers and rebuilds them into TagHelperBlock's.
- Added the code generator and corresponding chunk for a TagHelperBlock.
- Added syntax tree specific objects & helper methods to create accurate tag helper structures.

#71
Fix test to work with TH rewriters.

- Added understanding to the ParserTestBase for TagHelperBlock's
- Added a helper class MarkupTagHelperBlock to make building test TagHelpers easier.
- Fixed some existing tests that "new"d up the RazorParser and didn't obide by the new contract (to provide optimizers).

#71
Add tests to verify TagHelperParseTreeVisitor.

- Added tests to validate TagHelperParseTreeVisitor when dealing with valid HTML elements.

#71
Refactored CodeGeneratorContext to CodeBuilderContext.

- Needed to separate the context's of "generation" and "building" to enable the communication of the TagHelperProvider.
Add Microsoft.AspNet.Razor.Runtime src and test project.

#136
Create TagHelper specific C# code Generation.

- Added TagHelperChunk generation.
- Added CSharp visitors to understand TagHelperChunk's and render corresponding C# code.
- Added TagHelper specific metadata to the CodeGeneratorContext
- Refactored some code in the CSharpCodeVisitor so it could be utilized in other classes.

#72
Add several [NotNull] attributes.
Addressed code review comments
Add code generation tests for tag helpers.

#72
Addressed code review comments
Changed test tag helper temp names.
Add extensibility point for TH attribute code gen.

- Followed the "decorate" pattern that we use throughout Razor.
- Enabled the CSharpCodeBuilder to decorate the CSharpCodeVisitor which exposes a CSharpTagHelperCodeRenderer which is indirectly used to render attribute values.
- Fixed up some existing classes that just new'd up the CSharpCodeVisitor class to instead take in the decorated version.

#119
Add test for TagHelperAttributeCodeGenerator extensibility.

- Tested that we can successfully plugin our own TagHelperAttributeCodeGenerator.
- Moved some existing TagHelper test logic into its own base type to enhance code reusability.

#119
Add @addtaghelper directive.

- Also added some infrastructure pieces for it such as the ITagHelperDescriptorResolver and the default implementation TagHelperDescriptorResolver which will be filled out in a later commit.
- Reworked some extensibility points to allow accessibility of the descriptor resolvers per offline discussions.

#111
Add tests to validate @addtaghelper directive.

- Fixed existing tests to work with new RazorParser.
- Validated directive syntax tree creation, errors and code generation.

#111