Update appveyor.yml
Add AssemblyInformationalVersion attributes
Add note about continuous builds to readme.

Implements #50
Allow ToolBar button tooltips to be customised

Fixes #61. (thanks Camuvingian)
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
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 all Gemini projects to target .NET 4.5.

(.NET 4.5 was released in August 2012. It's time. And the TPL, which I
want to use, was improved in 4.5.)