Update 1-hello-world.md

- Typo fixes
- Added Xanga alongside LiveJournal, since it also launched in 1999, and was a popular blogging platform as well.
Typos fixes
Updates to Chapter 25

also the addition of some new images
Formatting corrections
Formatting corrections
Rename file
Formatting correction
File renaming
Line edits to Part 3
Formatting corrections
Formatting
Merge pull request #48 from cioccolato/fix02

Typo fixes in Part 1
Merge pull request #4 from WordPress/master

Update to latest WordPress/book