Upgrade NUnit to 2.6.3
Upgrade Caliburn.Micro to 2.0.1
Upgrade AvalonEdit to 4.4.2.9744
Upgrade HelixToolkit to 2014.2.423
Allow state file path to be overridden. Fixes #49
Fix toolbar binding failure when dragging

Fixes #67
Upgrade HelixToolkit to 2014.2.425
Upgrade Extended.Wpf.Toolkit to 2.3
Upgrade SharpDX to 2.6.2
Merge remote-tracking branch 'upstream/master'
Fix Extended.Wpf.Toolkit reference in Gemini.Demo.MonoGame
Missing file from previous commit
Fix SharpDX build issue caused by NuGet package restore running too late in the build process

(using solution from here: https://github.com/Tristyn/SharpDx-AppVeyor)
(In demo project) remove inherited properties from Inspector
Ensure CanExecute is called before invoking action from keyboard shortcut handler. Fixes #69.

Action.Invoke doesn't call guard method (CanExecute)
Add File > New menu item

with child menu items for each available file type, and extend
IEditorProvider to provide list of available file types. Implements #75
Update Pipes