Wrap README at 72 characters

That's what git does in commit messages. It improves readability in code
editors which usually are not configured to wrap lines by default.

Also, replace tabs with spaces in command examples so that they're
styled properly.

Change-Id: I7ee5aaf65f2f8f9a66a3802be06956d6c3005384
Update coding conventions in README

Remove obsolete text and replace it with a link to the new wiki page
with all the coding conventions.

Change-Id: Ida2bc9e46d91043229644da391ca0dc9e0b34ec8
Merge changes Ida2bc9e4,I7ee5aaf6

* changes:
  Update coding conventions in README
  Wrap README at 72 characters