Add line length autocorrect for blocks

[maxh]

Shortens long lines by inserting a line break into blocks like this:

# original
foo.bar { |baz| batbatbatbatbatbatbatbat(baz) }

# auto-corrected after this PR
foo.bar { |baz|
batbatbatbatbatbatbatbat(baz) }

# auto-corrected after other block alignment cops run
# (just one example -- final output depends on config)
foo.bar do |baz|
  batbatbatbatbatbatbatbat(baz)
end

---

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).
• 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.
• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Run bundle exec rake default. It executes all tests and RuboCop for itself, and generates the documentation.

[maxh]

I alpha ordered this list.

[bbatsov]

Thanks!