Removed Rakefile and replaced with Makefile

Tried to keep as much behaviour of the original as made sense.

The main justification for this is that I'm assuming more people will have `make` installed than `rake`/`ruby`.

Other options would just be to add `npm` scripts for these simple targets, removing the need for `make` entirely (happy to submit a PR for this if you like), or move to something like `grunt`, but that feels like overkill.