NCBI Mass Sequence Downlaoder v3.0

This is mostly a documentation update.
The project moved away from a simple README.md to readthedocs.org
The email address field was also removed since the NCBI documentation states that this should not be a user provided field, but rather the tool's developer email.

No binaries will be released for this version as v3.1 is just around the corner. The documentation upgrade was, however a significant change that warrants the need for a major version bump.