v1.5.3 Downgrade sqlalchemy-redshift, generate CLI docs, internal changes

What's Changed

• RM-49 Reduce field_to_sqlalchemy_type complexity by @ryantimjohn in #224
• RM-50 Simplify run_test into smaller functions by @Brunope in #229
• RM-65 Add sphinx argparse by @Brunope in #226
• Remove sphinx_requirements.txt - readthedocs build now uses setup.py by @Brunope in #225
• RM-46 Simplify redshift records_unload by @ryantimjohn in #227
• RM-43 Simplify records_mover-db-mysql-load_options.py by @ryantimjohn in #230
• RM-48 Simplify to_pandas_dtype by @ryantimjohn in #233
• RM-70 Cap sqlalchemy-redshift < 0.8.13 by @Brunope in #235
• RM-69 Remove bigfiles check by @Brunope in #232
• RM-56 Uncomment all requirements for deploy workflow in CircleCI by @ryantimjohn in #217

Full Changelog: v1.5.2...v1.5.3