Add verbose output for missing_samples

The output will now print which are the offending sample identifiers if
the -v flag is passed.

Fixes #89
Merge pull request #90 from ElDeveloper/issue_89

Add verbose output for missing_samples
Add remove_empty_rows to parse_otu_table

Previously this option was removed as it made the tests in Jenkins fail
because it was relying on QIIME 1.6.0.

Fixes #73
Merge pull request #92 from ElDeveloper/issue_73

Add remove_empty_rows to parse_otu_table