Ruby 2 encoding bug

An encoding bug broke the gem in Ruby 2.x.x.

```bash
/Users/Bookis/work/email_address_validator/lib/email_address_validator/rfc822-parser.rb:486: invalid multibyte escape: /\A(?-mix:[^\]\x00-\x20 \x7F\x80-\xFF()<>@,;:\\".\[]+)/ (SyntaxError)
invalid multibyte escape: /\A(?-mix:[^)\\\x0D\x80-\xFF(]+)/
invalid multibyte escape: /\A(?-mix:[^\]\\\x0D\x80-\xFF\[]+)/
invalid multibyte escape: /\A(?-mix:[^"\\\x0D\x80-\xFF]+)/
	from /Users/Bookis/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:51:in `require'
```