Use delta_ok to compare decimal numbers
Use get_member_by_rank() instead of next_member() in tests

This makes tests more robusts because they won't depend on the ordering of the hash keys anymore
Make sure that one can read communities with no species
Support for skipping writing empty communities
POD update
Hooks to read/write metacommunities
IO refactoring + now saving biom metacommunity name
Table role now records everything before -start_line
Support QIIME metacommunity name
More IO sanity checks
Excercise next_metacommunity and write_metacommunity in the tests for all formats
biom drivers now assigns taxonomy and weights
Small fixes