updated version to 1.6.0-dev
updated to 1.6.0-dev
Merge pull request #589 from gregcaporaso/160dev-update

160dev update - updated all version information to 1.6.0-dev
added sample_count_by_category
using natural sort now
Changed exception to option_parser.error
renamed to print_metadata_stats.py
fixed version
Merge pull request #591 from wasade/sample_count_by_category

added sample_count_by_category
Added new function mean_alpha and tests

This function allows to compute the mean alpha diversity data at a given
rarefaction depth.
Updated script to handle collated alpha data

Collated alpha diversity files can now be used with this script, the
user is now able to specify a given depth to get the mean of the values
added to the mapping file.
Merge pull request #596 from ElDeveloper/collated_alpha_map

Collated alpha map