Parsing part of body as header

Using version 2.5.4 and running the following script:

```
#!/usr/bin/env ruby
require 'mail'

mail = Mail.read_from_string(DATA.read)
puts mail

__END__
To: someone@example.org
Subject: Test Email

Foo: Bar

Baz
```

I get the following written to stderr:

```
WARNING: Could not parse (and so ignoring) ' Foo: Bar'
```

And stdout gives me:

```
Date: Fri, 15 Nov 2013 01:53:03 +0700
To: someone@example.org
Message-ID: <52851c0f95fa1_5e5d820711b011067@Swan.local.mail>
Subject: Test Email
Mime-Version: 1.0
Content-Type: text/plain;
charset=UTF-8
Content-Transfer-Encoding: 7bit
:

Baz
```

So it appears the first line of the body is parsed as an (empty) header.

Start by running the supplied Ruby script through Mail.read_from_string and trace how the parser handles the blank line before the body. Done means the indented “Foo: Bar” line remains body content, no parsing warning is emitted for it, and the resulting message preserves the body as shown.

Written by the indexing model from the issue text.