A store for TiddlyWeb for use in development.

A common problem with complicated web apps built on top of TiddlySpace
is that it is hard to do live development on a test or dev instance.
While the desired experience is to be able to edit tiddlers on the file
system and see those changes in the instance instantly, the current
habit is to make the changes, update the package, update the instance
then see the changes.

This store aims to fix that by providing a wrapper store that on 
tiddler_get first looks in a configured dir for an appropriate file
to satisfy the request.

Configuration is as follows:

    config = {
        'server_store': ['tiddlywebplugins.devstore2', {'devstore_root':
            './src'}],
        'wrapped_devstore': ['text', {'store_root': 'store'}],
        'log_level': 'DEBUG',
        }

Where devstore_root is either an absolute path or relative to whatever
the PWD is in the process using the config.

devstore uses tiddlywebplugins.twimport's url_to_tiddler and thus will
read files ending in .tid as a tiddler, .js as a javascript file or treat
other extensions as binary or pseuod-binary tiddlers.