Update control flow recommendation message

See 2740609a0fe0e58eb9f124f02960f4c05ba80795 and #185.
Merge pull request #200 from lee-dohm/message

Update control flow recommendation message
fix typos in README
Merge pull request #201 from nikai3d/patch-1

fix typos in README
Port BlockComments to Parser 2.0
Remove redundant message check
Fix a broken example
Use Parser::Base#tokenize instead of patching Parser::Lexer#advance.

We can remove some code for functionality that is now available
in Parser.
Provide file name to Parser to get better error messages.
Let Parser do the reading of files.

Instead of reading files into strings in RuboCop, we let Parser::Source::Buffer read the files. This decreases duplication of functionality.