Read from IO

[felipenoris]

Use case: Excel file inside a Zip or Gzip file.

[Arkoniak]

It would be nice to read xlsx directly from the web, without intermediate storage on a hard drive. Looking at the source it seems like it's doable:

1. XLSXFile should have an additional constructor (which accepts io instead of filepath)
2. read_or_open_xlsx should split itself based on the way how data is ingested.

Is it correct? Or something else is needed?

[felipenoris]

@Arkoniak, yes that is basically it. Feel free to send a PR on this. Maybe this will trigger a major refactoring.