Addin Improvements and Gist Integration Addin

• Save Encrypted .mdcrypt Extension Default
  When you save files as encrypted files, Markdown Monster now defaults to the new .mdcrypt extension to signify an encrypted file. MM still can open plain .md files that are encrypted, but the explicit extension makes it easy to see that the file requires a password to open.

• New Context Menu in Preview Browser
  The preview browser now provides a few options to show content in an external browser, and show source code in an editor window (with live HTML preview of the HTML text).

• Addin AddMenuItem() method
  You can now create new menu items from an addin more easily by using the new Addin.AddMenuItem() method. Allows insertion of a menu item before or after an existing item by name or caption.

• Addin OnInstall() and OnUninstall() methods
  Addins now get a couple of additional methods to handle post installation and pre-uninstallation tasks. These methods allow installation and removal of additional resources.

• Update Github Gist Integration Addin
  Added the Gist Integration Addin to allow loading and saving of documents from Gists. New File menu options for Load from Gist and Save as Gist let you manage both markdown and other code documents through online Gists.