Fix var_dir -> var_path typo in app.js.

The typo actually crashes the app when running node v0.10.5, which makes
`path.join()` check its arguments and ensure that they're all strings.
got rid of the var_path static middleware, as per brian and mike talk.
Merge pull request #854 from toolness/development

Fix var_dir -> var_path typo in app.js.