Add Lint/MultipleCompare cop

[pocke]

In Ruby, the following code raises an error.

x = 20
0 < x < 100 # => NoMethodError: undefined method `<' for true:TrueClass

The error is confusing for beginner and Python programmer.

This cop suggests and autocorrects the following code instead.

x = 20
0 < x && x < 100

---

Before submitting the PR make sure the following are checked:

• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Used the same coding conventions as the rest of the project.
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Added an entry to the Changelog if the new code introduces user-observable changes. See changelog entry format.
• All tests are passing.
• The new code doesn't generate RuboCop offenses.
• The PR relates to only one subject with a clear title
  and description in grammatically correct, complete sentences.
• Updated cop documentation with rake generate_cops_documentation (required only when you've added a new cop or changed the configuration/documentation of an existing cop).

[bbatsov]

👍