Added a virtual surface that can be panned and zoomed by the user, typically in 'hide code' mode.  This is useful for exploring fractals and other procedural textures that are too large to be fully explored by simple mouse position alone.  Care was taken to preserve backwards compatibility, so legacy shaders will still work as they always did, and new shaders need not be aware of the virtual surface if they don't care to use it.
Remove incorrect keyword gl_Vertex (the correct keyword is gl_Position, but it's only for vertex shaders, and our code editor only shows fragment shaders, so this keyword is removed entirely).
Fix some issues with the new virtual surface.  Added a reset feature: use shift-click on the canvas to reset the surface to its center position and zoom.  Also, auto-reset the surface position prior to capturing thumbnails for the gallery.
Comment out a toolbar eventhandler that is causing a bug with CodeMirror.  Hopfully this is temporary until I find a better solution.
Added a better solution to the toolbar/pan issue.
Adjust tooltip on pan/zoom button.
Added jsdifflib to show the difference between versions.
Fix typo
Remove unused code
Fixed various issues with diff.
Styling and parent fixes for diff.
Update the diff color scheme to be similar to the rest of the site.
Tweak the diff theme.
More diff bugfixes.
Merge pull request #7 from emackey/master

Slidable surface, and jsdiff with parent
Attempting to fix the "black bars" problem seen on Macs.  Noticed that the Mac assigns vertex attributes in a different order from other platforms, so assuming that "attribute vec3 position" is the same attribute ID in both vertex shaders is no longer a valid assumption.  Added code to track the attribute IDs separately.
Fixing the fix
Merge pull request #8 from emackey/master

Fixed the black bars seen on Mac
Very old shaders have the owner set to false, these shaders should always be forked, not saved from now on.
Merge pull request #9 from emackey/fork-orphans

Add 'fork' button to old shaders