Add GET_CHUNK_URL option

[levic]

Currently we use django-compress to handle & cache busting. This is quite the overkill if the JS/CSS has already been processed using webpack.

The following patch allows you to change how django-webpack-loader generates output URLs -- allowing you to provide your own cache busting (or any other alteration to output URLs you might want).

This patch is intended to be a proof of concept; if you're happy with this approach then I'll implement test cases & add documentation.

[levic]

The resolution of GET_CHUNK_URL from a string is done on-demand; it could be done when loading webpack_loader.utils but I did this to be tolerant of module loading order (if an implementation of GET_CHUNK_URL tries to import webpack_loader.utils you will get problems)

[owais]

@levic I've changed the internal implementation to a class based one. Please check it out. If you still need this, you can add a simple setting called LOADER_CLASS to settings and use that class instead of the inbuilt webpack_loader.loader.WebpackLoader class. The class already has a method named get_chunk_url which can be overridden to allow custom logic.

Thanks

[owais]

Closing this as the internal implementation has changed and this PR is not useful now. Really sorry about that. Feel free to open a new one against latest revision.

[levic]

Thanks; have updated my code and will post another pull request once have tested it a bit more