Superquery

Updates included:

* Fixes some minor issues with Client state, flow and reusing a connection
* Simplifies the public interface of Client (hiding some lower level set methods)
* Changes console output from using print to timestamped logging
* Implements result.to_df()
* Updates the documentation and examples

This version supports the previous version's query API, as well as a new API that is aligned with BigQuery. This means minimal changes to your current codebase if you want to swap over to using superQuery's library.

Now you can set your own projectId!

You can now choose the hostname of the proxy to which you want to connect. This will typically always be proxy.superquery.io but makes provision for others.