Bug 1029967 - rewrite Makefile in email app in javascript

It would be good to see a `removeFile` function helper for encapsulating the multiple steps to remove a file. That would allow the removal of tmpl_builder.js and .jshintrc to be one line entries in `execute` too (see async promise comments in the `execute` comments. It would be nice to group all the file deletes in one section too.