Upgrade codemirror to current master
Prioritize "module.exports" over "exports" in require sandbox
  (Node-ism, inherited (temporarily?) to support codemirror upgrade)
Fix up codemirror instructions to match new paths in config example
Fixes for running TiddlyWiki on node-webkit

See Jermolene/TiddlyWiki5NodeWebkit
Improve TiddlyWiki as a library

1. Make it possible to disable specific boot tasks
2. Extend the startup mechanism to allow startup tasks to be disabled

Again, see Jermolene/TiddlyWiki5NodeWebkit to see how these features
fit together.
Fix incorrect filter in shadow $:/DefaultTiddlers

Fixes #606
Merge pull request #604 from natecain/module_exports

Module exports
Pass content-type to codemirror mode option for syntax highlight

Fixes #605
Restored drag and drop functionality within TEXTAREAs and INPUTs

As mentioned by @Skeeve in #592
Remove erroneous global wiki references

$tw.wiki is used as a global reference in the outer initialisation
modules. It shouldn’t be used in widgets etc.