"an email should have been sent with" step behaves incorrectly when not specifying headers

[foobear]

The an email should have been sent with: step always considers everything until the first \n\n to be headers. It ignores any lines that do not match the header style, so when given only a message body, it ignores anything until the first \n\n.

Example:

Then an email should have been sent with:
  """
  Hello
  
  Bye
  """

This passes for an email where the body is only "Bye".

I suggest raising an error when encountering an invalid header line, or considering the entire string as the message body, if the headers section does not contain header-link lines.

[FLeinzi]

I made a pull request for this issue: #158

We will now interpret all lines as body when not specifying headers.