Proposal: Add a basic HTTP Client chapter to UPBE

[dmitrizagidulin]

(Extracted from #133)
A reader who finishes UPBE currently encounters some very advanced topics (GUI building with Morphic, advanced web applications with Seaside, reflections and meta-programming, etc), but cannot do some basic operations, such as read data from a file, or get some data via an HTTP REST API (or even scrape it off a web page).

Let's add a basic 'Interacting with HTTP' chapter (we could move the Zinc HTTP Client chapter from Enterprise Pharo into this book, for example). It would cover some frequently-encountered beginner topics like "Here's how to do an HTTP GET request to fetch a Twitter message" or "Here's how to make a POST to a web API".

Reasons to add an HTTP client chapter to UPBE:

1. It is crucial beginner functionality. Much more so than full-scale web applications (like the Seaside chapter) or desktop GUIs.
2. It addresses a common misconception about Smalltalk/Pharo, which is that it is "isolated" or "doesn't play well with others". As long as we show that you can easily work with HTTP APIs in Pharo, it means that Pharo has as much inter-op as any other language.

[Ducasse]

Pay attention the best is the enemy of done. I prefer a UPBE done even if missing some chapters that a 95% finished one. For example the spanish translation was nearly finished and it stayed at 98% during 1,5 year. I finished it while I do not speak or write spanish. Same with the translation of the etoy book.
The seaside chapter is a little self contained tutorial and it is good as it is.
A guy wants to get started he can follow and get done. If he wants to know more then he will read the full Seaside book.
Now there is no mention of Seaside in the web perspective book because Seaside as a full book.
In UPBE you could move the Build a web App with rest from WebPerspective but I would not move any of Zinc and I would not move FileSystem because these chapters are not tutorial. there are more reference manual. Now you can sketch some information about files.
we could remove the regex from UPBE because I was not aware that there is a duplication.
You are probably reading the Omnibus version of PBE. (the omnibus version was made by oscar for his lecture).