Version 3.0.3

Various bugfixes and improvements:

1. is_proofread (which is also used for connectivity queries) should now work with the public release data (see docstring for details)
2. get_cave_table will now optionally add user details (unclear if this works on public data)
3. various fixes for get_somas, find_mat_version, is_valid_root and is_latest_root