Add centralised theme

Fix #110
Add a popping animation to the tags editor
Use pop animation for the view mode tag list

Works well with the task management demo
Now trying out applying the pop animation to the open tiddler list
Adopt hipsterish skinny font weights
Fixed problem with tags that appear more than once in the tag string
Skinnify headings
Allow tag tiddlers to specify the title of an icon tiddler

Demonstrated on the "done" tag
Add some more methods to the fake DOM

These methods are needed to get static saving working in the browser
again (click "Save Static" in the Demo tiddler)
Skinnify tab labels
Fix problem with pop listview animation

It turns out the transitionEnd event fires separately for each animated
property. We'll just remove ourselves on the first one
A better green for the "done" tag
Linting
Update animations to use a timer instead the transitionEnd event

Thr trouble is that the transitionEnd event doesn't fire under some
circumstances (eg if the animated element is hidden). So, it's more
reliable to use a timer instead
Display optional tiddler icon before title

Just set the 'icon' field of the tiddler to the title of an image. (See
the "done" tiddler for an example)
Fix problem with Sticky Titles theme
Make the info dropdown work properly with sticky titles
Refactor scroller so that the scrollIntoView() method is a bit more usable

Passing an event instead of a DOM node was silly.
Special treatment so that text reference to title field works for missing tiddlers

The title field is the one field that we know for missing tiddlers.

This is needed in a subsequent commit of viewswitcher.
Add a hack to switch slowmo animation mode

Just type `$tw.slowmo()` in the developer console to engage slowmo mode.