Import docs from Google Code Archive

[hugovk]

The README says:

This tutorial is distributed with PrettyTable and is meant to serve
as a "quick start" guide for the lazy or impatient. It is not an
exhaustive description of the whole API, and it is not guaranteed to be
100% up to date. For more complete and update documentation, check the
PrettyTable wiki.

The wiki is on the old Google Code Archive:

• https://code.google.com/archive/p/prettytable/wikis

And links to two pages:

• https://code.google.com/archive/p/prettytable/wikis/Tutorial.wiki
• https://code.google.com/archive/p/prettytable/wikis/Installation.wiki

Let's move those to this repo as versioned MD or RST files.

There may be some overlap between the tutorial and the README, if so, perhaps they could be merged. Or create a new file for it.

Installation is short and out of date, it says to use easy_install, or to manually copy the file to certain directories for different operating systems (with python2.5 in the examples!). This could be replaced with modern pip install ... info near the top of the README.

[andreykurilin]

@hugovk cloud.google.com stores these pages in markdown. Here is Tutorial.wiki.
I tried to quickly compare the sections of ReadMe and Tutorial page: they provide the similar info (ReadMe misses information about from_html method).
As for installation - I guess, there is no reason to import Installation.wiki page. It can be rewritten with one command that should cover all modern systems pip install PrettyTable :)

[hugovk]

@andreykurilin Thank you very much for checking! I think we probably remove the link in the README to the wiki then.

Yeah, pip install PrettyTable can replace Installation.wiki! :)