ENH: tilde expansion for write functions, #11438
closes #11438 
Added calls to `_expand_user()` in multiple Formatter classes so that writer functions, such as `to_csv()` and `to_html()`, can perform tilde expansion on file paths beginning `~/`. This makes the writer functions consistent with the reader functions, such as `read_csv()`. I also changed the `__init__()` for `CSVFormatter` to conform to the pep8 width limit.
