some prompts for the README

[paddymul]

closes #xxx

[paddymul]

I was trying to understand the project, the documentation is written to people who know they want to import data from tableau and tableauhyperapi isn't fast enough for them.

There is a much wider potential audience for this library. What about the people who know pandas and know tableau, how do you sell them or the potential if they land on this README/docs?

[WillAyd]

I was trying to understand the project, the documentation is written to people who know they want to import data from tableau and tableauhyperapi isn't fast enough for them.

Performance is definitely a selling point, though the others are:

1. Less lines of code
2. Lossless Type Exchange
3. Easy exchange of Geographic data
4. Out-of-core / larger-than-RAM streaming support
5. Free!

The free aspect is easy to take for granted in the open source space, but can be a major selling point for organizations that don't want to purchase Tableau Prep. I also hear that it is better and easier to use than that, although that is subjective, and I want to be careful how we compare the project to Prep