Fix formatting, code errors and indentation in README

This is done:

* Most importantly, the 2nd half of the README has broken formatting due to the line that starts with triple backticks (``` ` ` `start_cmds` ` `:``` but whithout the spaces, line 189) which turns the rest of the file inte one huge code block. I replace these with a single-backticks (``` `start_cmds` ```).
* Adds syntax highlinting to Erlang code examples.
* Fix indentation of code so that it looks OK in github web view. (Replaces tabs by spaces).
* In a few cases, adds a missing closing square bracket to fix syntax error in code examples.
* Removes trailing whitespace.