Update README.md

add another case for use unless case. I saw in many places something like: 'if not current_user'. I think it's a bad way to do that.
Prefer first and last over [0] and [-1]
Single line class definition utilize Class.new

The Class.new version is a cleaner syntax and removes the unwanted `;` that is included in the default class syntax.
Merge pull request #174 from adkron/single_line_class

Single line class definition utilize Class.new
Refine lambda syntax rule
Prefer proc over Proc.new
Merge pull request #173 from jdalbert/array_access

Prefer first and last over [0] and [-1]
Update README.md

add only 'if not' example
Merge pull request #171 from lucianosousa/patch-1

Add more examples for use unless case
Add rule for method calls without args (fixes #145)
Mention HEREDOC stripping technique (fixes #72)
Expand examples for parens and defining methods
Merge pull request #177 from mark-rushakoff/def-parens

Expand examples for parens and defining methods
Update starting quote
Discourage explicit use of the === operator
Remove some conflicting advice
Clean up grammar in method missing recommendations
Merge pull request #180 from lee-dohm/master

Clean up grammar in method missing recommendations
Put condition on same line as if/unless
Merge pull request #182 from mark-rushakoff/if-condition-line

Put condition on same line as if/unless