to_csv  - allow to create folders.
currently `to_csv ` will create a file if it does not exist. However it will not create a folder (nor sub-folders).
In this case it will raise 
`IOError: [Errno 2] No such file or directory:`

The user must wrap his code in order for it to create a folder.

I'm not sure why the function behaves like this.. It would be great if it will also create folders if needed.

Reference from stack overflow:
https://stackoverflow.com/questions/47143836/pandas-dataframe-to-csv-raising-ioerror-no-such-file-or-directory
