[skip ci]

Ref: https://rawgit.com/ "RawGit has reached the end of its useful life"
Ref: https://news.ycombinator.com/item?id=18202481
Closes https://github.com/curl/curl/pull/3131

- replace tabs with spaces where possible
- remove line ending spaces
- remove double/triple newlines at EOF
- fix a non-UTF-8 character
- cleanup a few indentations/line continuations
  in manual examples

Closes https://github.com/curl/curl/pull/3037

Closes #2913

Closes #2857

Closes #2484

s/off/from

Closes #2300

Closes #2069

rawgit.com asks to use the domain cdn.rawgit.com for production

See #900

Closes #834

It also makes it less readable as plain text, so let's keep this
primarily for github use.

Removed the top ascii art logo, as it looks weird when markdownified.

Attempt to make it look more appealing on github