Moved @addtaghelper to ViewStart.

- Updated project.json to have a valid webroot. Webroot isn't pointing to the specific folder because the TagHelperSample has no valid content for the webroot yet.

samples/TagHelperSample.Web/Views/Home/Create.cshtml

@@ -1,7 +1,6 @@
 
 @using TagHelperSample.Web.Models
 @model User
-@addtaghelper "Microsoft.AspNet.Mvc.TagHelpers"
 
 <h2>Create</h2>
 

samples/TagHelperSample.Web/Views/Home/Edit.cshtml

@@ -1,7 +1,6 @@
 
 @using TagHelperSample.Web.Models
 @model User
-@addtaghelper "Microsoft.AspNet.Mvc.TagHelpers"
 
 <h2>Edit</h2>
 

samples/TagHelperSample.Web/Views/Home/Index.cshtml

@@ -1,7 +1,6 @@
 
 @using TagHelperSample.Web.Models
 @model IEnumerable<User>
-@addtaghelper "Microsoft.AspNet.Mvc.TagHelpers"
 
 <h2>Index</h2>
 <p>

samples/TagHelperSample.Web/Views/_ViewStart.cshtml

@@ -0,0 +1 @@
+@addtaghelper "Microsoft.AspNet.Mvc.TagHelpers"

samples/TagHelperSample.Web/project.json

@@ -1,4 +1,5 @@
 {
+  "webroot": ".",
   "compilationOptions": {
     "warningsAsErrors": true
   },