porting per_library_stats.py from QIIME
first non-qiime-dependent version of print_biom_table_summary.py
cleaned up language

all occurrences of "OTU" replaced with "Observation", and differentiated between observations and counts.
added test of new compute_counts_per_sample_stats function
added additional test and changed parameter name
several new features

now prints the md5sum of the input table, and supports input of gzipped biom files.
fixed bug where script would traceback without any input
adding doc for print_biom_table_summary.py
added test for safe_md5
Merge pull request #103 from gregcaporaso/102

added print_biom_table_summary.py