Port tests from Katana.
Updating release Nuget.config
Updating dev Nuget.config
Removed source files from the project
Reacting to System.IO.FileSystem package version change
Reacting to System.IO package version change
Fixing PhysicalFileSystem to treat absolute paths correctly
* Additionally fix PhysicalFileSystemTests to use
  IApplicationEnvironment.ApplicationBasePath

Fixes #14
Changing case for project.json
Adding TryGetParentPath to IFileSystem

Fixes #12
Updated to use the new target framework in project.json
Change how we resolve the root directory
- Read the application base from IApplicationEnvironment
  when running in the KRuntime
Removed unused PlatformHelper.cs
Updated build.cmd
Changed ApplicationContext to AppContext
Cross compiled to aspnet50 as well as net45
Removed AppContext usage
#17 - Remove smart-auto-base-path logic, it breaks razor. Use absolute paths.
Block relative paths.
Removed unused dependency
Updating release NuGet.config