get_seq_ids_from_seq_id_file, skip blank lines

Fixes #1576
Add test for get_seq_ids_from_seq_id_file

This function was previously untested, now there are tests. Test data includes
input file consisting of blank lines.
PEP8 Fixes
Merge pull request #1577 from adamrp/issue-1576

Issue 1576
Merge branch 'master' into test_port
Removed unused test