A bunch of little changes that together enable external image support.
Try:
```
tiddlywiki editions/tw5.com --verbose --build externalimages
```
Then open `externalimages.html`, look for the images in the more/types
tab of the sidebar, open them and verify that they are set with an
external SRC attribute, not a data URI.
The issue was that rendertiddlers always clears the output folder,
which meant that it was overwriting anything previously output by the
rendertiddler command.
Still quite a few details to work out, but this shows the basic idea of
re-using the theme mechanism to handle language plugins.
Comments and questions welcome.
Select the new "Sticky Titles" theme to cause tiddler titles to stick
to the top of the window as you scroll. It works very well in Chrome
Canary, reasonably well in iOS 7.
As an aside, it would be nice to be able to package this is as
something a bit smaller than a theme; maybe themes need to have
optional hacks that can be associated with them.
No UI for switching themes yet, try these two commands in the console:
`$tw.wiki.addTiddler({title:"$:/theme",
text:"$:/themes/tiddlywiki/starlight"})`
and
`$tw.wiki.addTiddler({title:"$:/theme",
text:"$:/themes/tiddlywiki/snowwhite"})`
To start with, we move the current stylesheets into a theme plugin
called "Snow White". Wikis have to specify at least one theme in their
`tiddlywiki.info` file. Next we'll add a mechanism for switching
between loaded themes
