Define GET /reference/{id}/bases in favor of GAReference.sequence.

This approach is intended to allow for more efficient access to the bases needed by the client. Returning an upwards of 300MB (uncompressed) string as a single JSON value would likely have performance issues; this is solved here via pagination if the endpoint chooses to implement the method with multiple pages.
This will just be the start position of the request, no? Or, will the API return fragments of the reference where each fragment will contain a different offset?