Reorganization of epub JS modules and build system for RequireJS/AMD, support for remote zipped EPUB files using partial HTTP fetching

Hi!

This pull request contains both reorganization of JS modules to employ Asynchronous Module Definition using RequireJS and experimental support for fetching from remote zipped EPUB packages using HTTP Range Requests / Partial Responses (also known as byte serving), including support for fixed layout SVG pages (that was absent from the previous experimental work pulled onto the http-byte-range-experiment branch).

The rake build system has also been radically simplified and made to use built-in inter-task dependency mechanisms of rake.