Reduce npm package bloat

[strager]

• ejs pulls in a bunch: Fix #510. Remove jake dev dependency and embed arg parser. mde/ejs#645
• svg-sprite pulls in a bunch
• cssstyle uses an old version of cssom
• jsdom pulls in everything

[strager]

We only use jsdom for testing the web demo marking code. We could just drop testing for that code, or we could switch to another implementation (e.g. refs/archive/web-demo-absolute-marking, which jsdom can't test anyway).

[strager]

jsdom dropped in 830df6b (after removing its need in commit e7c6c79).