Removing out var usage
Updating CSharpCodeVisitor to generate implicit expressions on a single
line

Fixing 151
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
Rebased onto latest dev.

- Fixed tag helper parse tree visitor rebase error.
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
Addressed code review comments.
Addressed code review comments.
Added support for @helper and @section.
Disabled instrumentation in writing scopes.
Fix declaration visitor to dive into blocks.
Addressed code review comments