Checklist of tasks to improve multiple morph functionality #84

To be fixed in branch morph_sequence

• Replace --temperature with --sort-by=FIELD
• Add --reverse tag
• Add --metadata-filename; a user can store FIELD data in that metadata file which PDFmorph can read from
• Add --verbose tag to condense output
• Make multiple_morphs and single_morphs functions more maintainable

To be fixed in in branch change_libraries

• Move to Pytest rather than Unittest
• Refactor test file names to specify which module is being tested
• Fix deprecation with pkg_resources