A few simple fixes and enhancements

* Error output from jade
* Add an appendix to flowtime slides
* Close the outermost flowtime div
I assume the purpose of this appendix is to inject HTML at the end of the file (e.g. to load scripts, add more markup, etc)?

If so, you need to document it in `lib/main.js` in the `getMetadata` function (specifically, the `defaults' variable) and give it a default value AND add it to the `Metadata.md` file.