updated default quoting on to_csv function to csv.QUOTE_NONNUMERIC
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

@ayang2012 : Thanks for submitting this PR!  A lot to unpack here, but the biggest question is:

This is an API change.  Can you explain what the rationale is for the change?

(FYI: to anyone else reviewing this, I know there are a bunch of other things to comment on, but this is ultimately the question I want answered before we dive into the other details) @ayang2012 can you comment on https://github.com/pandas-dev/pandas/pull/27965#issuecomment-522290097? Closing as I don't think we necessarily want to do this, but certainly open to discussion on it. @ayang2012 if you do think something needs to be changed with this I think best to open an issue and we can discuss appetite / approach up front as required