Refactor - build system sucks

[kumavis]

it sucks.

simplified description of build requirements:

• make a build dir (empty it if its present)
• dump some static files into a certain place e.g. images
• compile some ejs into an html file
• compile some sass into a css file
• compile some ember templates into a js file (minify if prod)
• browserify the app entry-point into a js file (with browserify debug flag if a dev build) (minify if prod)
• (when a dev build) rerun a build process if a related file changed