Libhxl Python Versions Save

• make logup log level configurable via environment variable

• update URLs for test files on GitHub
• fixed bug in aggregators that excluded tag patterns ending in "!"

• reduce log level for failed number conversion from INFO to DEBUG

• remove pytest from requirements.txt, and move it to tests_require in setup.py

Minor update:

• allow .hxl extension for CSV data
• change hxlspec script args to allow variable input source

• loosen versions for dependencies
• remove dependency on requests_cache

• milestone release
• fix URL munging for direct-download HXL Proxy URLs
• add hxlinfo command-line script
• added headers and hxl_headers fields to output of hxl.input.info()

• remove hxl.input.ExcelInput.info() and make a top-level hxl.input.info() function that works with every data type (also alias to hxl.info())
• update Makefile for new git branch structure (just dev and prod)

• update requirements to allow latest versions of dependencies
• don't fall back to CSV if we have a MIME type or file extension that's not in the allow list (which is fairly liberal)
• change behaviour of ReplaceDataFilter so that with a map, it stops after the first successful replacement for each value
• change to ReplaceDataFilter means that replacement maps can now have default values at the end
• speed up ReplaceDataFilter by precompiling matching column indices for each pattern/replacement
• simplify Excel handling to remove dependency on mmap and tmpfile
• add patch from wynnw to fix crash reading some local files
• fixed issue where libhxl can't read directly from sys.stdin