v3.1.0 - fix reports summary writing

[jethror1]

• fix returning BAM files excluded from CNV calling as list of file names instead of describe details
  • fixes #191
• add additional unit tests to better test report summary writing

---

This change is 

[pep8speaks]

Hello @jethror1! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file resources/home/dnanexus/dias_batch/tests/test_dx_requests.py:

Line 1260:5: E303 too many blank lines (2)

• In the file resources/home/dnanexus/dias_batch/tests/test_utils.py:

Line 297:5: E303 too many blank lines (2)